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mediocre-blog/assets/viz/1/goog/string/string.js
Brian Picciano 4598d7092b add viz 1 post
2018-11-12 15:29:55 -05:00

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// Copyright 2006 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Utilities for string manipulation.
* @author arv@google.com (Erik Arvidsson)
*/
/**
* Namespace for string utilities
*/
goog.provide('goog.string');
goog.provide('goog.string.Unicode');
/**
* @define {boolean} Enables HTML escaping of lowercase letter "e" which helps
* with detection of double-escaping as this letter is frequently used.
*/
goog.define('goog.string.DETECT_DOUBLE_ESCAPING', false);
/**
* @define {boolean} Whether to force non-dom html unescaping.
*/
goog.define('goog.string.FORCE_NON_DOM_HTML_UNESCAPING', false);
/**
* Common Unicode string characters.
* @enum {string}
*/
goog.string.Unicode = {
NBSP: '\xa0'
};
/**
* Fast prefix-checker.
* @param {string} str The string to check.
* @param {string} prefix A string to look for at the start of {@code str}.
* @return {boolean} True if {@code str} begins with {@code prefix}.
*/
goog.string.startsWith = function(str, prefix) {
return str.lastIndexOf(prefix, 0) == 0;
};
/**
* Fast suffix-checker.
* @param {string} str The string to check.
* @param {string} suffix A string to look for at the end of {@code str}.
* @return {boolean} True if {@code str} ends with {@code suffix}.
*/
goog.string.endsWith = function(str, suffix) {
var l = str.length - suffix.length;
return l >= 0 && str.indexOf(suffix, l) == l;
};
/**
* Case-insensitive prefix-checker.
* @param {string} str The string to check.
* @param {string} prefix A string to look for at the end of {@code str}.
* @return {boolean} True if {@code str} begins with {@code prefix} (ignoring
* case).
*/
goog.string.caseInsensitiveStartsWith = function(str, prefix) {
return goog.string.caseInsensitiveCompare(
prefix, str.substr(0, prefix.length)) == 0;
};
/**
* Case-insensitive suffix-checker.
* @param {string} str The string to check.
* @param {string} suffix A string to look for at the end of {@code str}.
* @return {boolean} True if {@code str} ends with {@code suffix} (ignoring
* case).
*/
goog.string.caseInsensitiveEndsWith = function(str, suffix) {
return goog.string.caseInsensitiveCompare(
suffix, str.substr(str.length - suffix.length, suffix.length)) ==
0;
};
/**
* Case-insensitive equality checker.
* @param {string} str1 First string to check.
* @param {string} str2 Second string to check.
* @return {boolean} True if {@code str1} and {@code str2} are the same string,
* ignoring case.
*/
goog.string.caseInsensitiveEquals = function(str1, str2) {
return str1.toLowerCase() == str2.toLowerCase();
};
/**
* Does simple python-style string substitution.
* subs("foo%s hot%s", "bar", "dog") becomes "foobar hotdog".
* @param {string} str The string containing the pattern.
* @param {...*} var_args The items to substitute into the pattern.
* @return {string} A copy of {@code str} in which each occurrence of
* {@code %s} has been replaced an argument from {@code var_args}.
*/
goog.string.subs = function(str, var_args) {
var splitParts = str.split('%s');
var returnString = '';
var subsArguments = Array.prototype.slice.call(arguments, 1);
while (subsArguments.length &&
// Replace up to the last split part. We are inserting in the
// positions between split parts.
splitParts.length > 1) {
returnString += splitParts.shift() + subsArguments.shift();
}
return returnString + splitParts.join('%s'); // Join unused '%s'
};
/**
* Converts multiple whitespace chars (spaces, non-breaking-spaces, new lines
* and tabs) to a single space, and strips leading and trailing whitespace.
* @param {string} str Input string.
* @return {string} A copy of {@code str} with collapsed whitespace.
*/
goog.string.collapseWhitespace = function(str) {
// Since IE doesn't include non-breaking-space (0xa0) in their \s character
// class (as required by section 7.2 of the ECMAScript spec), we explicitly
// include it in the regexp to enforce consistent cross-browser behavior.
return str.replace(/[\s\xa0]+/g, ' ').replace(/^\s+|\s+$/g, '');
};
/**
* Checks if a string is empty or contains only whitespaces.
* @param {string} str The string to check.
* @return {boolean} Whether {@code str} is empty or whitespace only.
*/
goog.string.isEmptyOrWhitespace = function(str) {
// testing length == 0 first is actually slower in all browsers (about the
// same in Opera).
// Since IE doesn't include non-breaking-space (0xa0) in their \s character
// class (as required by section 7.2 of the ECMAScript spec), we explicitly
// include it in the regexp to enforce consistent cross-browser behavior.
return /^[\s\xa0]*$/.test(str);
};
/**
* Checks if a string is empty.
* @param {string} str The string to check.
* @return {boolean} Whether {@code str} is empty.
*/
goog.string.isEmptyString = function(str) {
return str.length == 0;
};
/**
* Checks if a string is empty or contains only whitespaces.
*
* TODO(user): Deprecate this when clients have been switched over to
* goog.string.isEmptyOrWhitespace.
*
* @param {string} str The string to check.
* @return {boolean} Whether {@code str} is empty or whitespace only.
*/
goog.string.isEmpty = goog.string.isEmptyOrWhitespace;
/**
* Checks if a string is null, undefined, empty or contains only whitespaces.
* @param {*} str The string to check.
* @return {boolean} Whether {@code str} is null, undefined, empty, or
* whitespace only.
* @deprecated Use goog.string.isEmptyOrWhitespace(goog.string.makeSafe(str))
* instead.
*/
goog.string.isEmptyOrWhitespaceSafe = function(str) {
return goog.string.isEmptyOrWhitespace(goog.string.makeSafe(str));
};
/**
* Checks if a string is null, undefined, empty or contains only whitespaces.
*
* TODO(user): Deprecate this when clients have been switched over to
* goog.string.isEmptyOrWhitespaceSafe.
*
* @param {*} str The string to check.
* @return {boolean} Whether {@code str} is null, undefined, empty, or
* whitespace only.
*/
goog.string.isEmptySafe = goog.string.isEmptyOrWhitespaceSafe;
/**
* Checks if a string is all breaking whitespace.
* @param {string} str The string to check.
* @return {boolean} Whether the string is all breaking whitespace.
*/
goog.string.isBreakingWhitespace = function(str) {
return !/[^\t\n\r ]/.test(str);
};
/**
* Checks if a string contains all letters.
* @param {string} str string to check.
* @return {boolean} True if {@code str} consists entirely of letters.
*/
goog.string.isAlpha = function(str) {
return !/[^a-zA-Z]/.test(str);
};
/**
* Checks if a string contains only numbers.
* @param {*} str string to check. If not a string, it will be
* casted to one.
* @return {boolean} True if {@code str} is numeric.
*/
goog.string.isNumeric = function(str) {
return !/[^0-9]/.test(str);
};
/**
* Checks if a string contains only numbers or letters.
* @param {string} str string to check.
* @return {boolean} True if {@code str} is alphanumeric.
*/
goog.string.isAlphaNumeric = function(str) {
return !/[^a-zA-Z0-9]/.test(str);
};
/**
* Checks if a character is a space character.
* @param {string} ch Character to check.
* @return {boolean} True if {@code ch} is a space.
*/
goog.string.isSpace = function(ch) {
return ch == ' ';
};
/**
* Checks if a character is a valid unicode character.
* @param {string} ch Character to check.
* @return {boolean} True if {@code ch} is a valid unicode character.
*/
goog.string.isUnicodeChar = function(ch) {
return ch.length == 1 && ch >= ' ' && ch <= '~' ||
ch >= '\u0080' && ch <= '\uFFFD';
};
/**
* Takes a string and replaces newlines with a space. Multiple lines are
* replaced with a single space.
* @param {string} str The string from which to strip newlines.
* @return {string} A copy of {@code str} stripped of newlines.
*/
goog.string.stripNewlines = function(str) {
return str.replace(/(\r\n|\r|\n)+/g, ' ');
};
/**
* Replaces Windows and Mac new lines with unix style: \r or \r\n with \n.
* @param {string} str The string to in which to canonicalize newlines.
* @return {string} {@code str} A copy of {@code} with canonicalized newlines.
*/
goog.string.canonicalizeNewlines = function(str) {
return str.replace(/(\r\n|\r|\n)/g, '\n');
};
/**
* Normalizes whitespace in a string, replacing all whitespace chars with
* a space.
* @param {string} str The string in which to normalize whitespace.
* @return {string} A copy of {@code str} with all whitespace normalized.
*/
goog.string.normalizeWhitespace = function(str) {
return str.replace(/\xa0|\s/g, ' ');
};
/**
* Normalizes spaces in a string, replacing all consecutive spaces and tabs
* with a single space. Replaces non-breaking space with a space.
* @param {string} str The string in which to normalize spaces.
* @return {string} A copy of {@code str} with all consecutive spaces and tabs
* replaced with a single space.
*/
goog.string.normalizeSpaces = function(str) {
return str.replace(/\xa0|[ \t]+/g, ' ');
};
/**
* Removes the breaking spaces from the left and right of the string and
* collapses the sequences of breaking spaces in the middle into single spaces.
* The original and the result strings render the same way in HTML.
* @param {string} str A string in which to collapse spaces.
* @return {string} Copy of the string with normalized breaking spaces.
*/
goog.string.collapseBreakingSpaces = function(str) {
return str.replace(/[\t\r\n ]+/g, ' ')
.replace(/^[\t\r\n ]+|[\t\r\n ]+$/g, '');
};
/**
* Trims white spaces to the left and right of a string.
* @param {string} str The string to trim.
* @return {string} A trimmed copy of {@code str}.
*/
goog.string.trim =
(goog.TRUSTED_SITE && String.prototype.trim) ? function(str) {
return str.trim();
} : function(str) {
// Since IE doesn't include non-breaking-space (0xa0) in their \s
// character class (as required by section 7.2 of the ECMAScript spec),
// we explicitly include it in the regexp to enforce consistent
// cross-browser behavior.
return str.replace(/^[\s\xa0]+|[\s\xa0]+$/g, '');
};
/**
* Trims whitespaces at the left end of a string.
* @param {string} str The string to left trim.
* @return {string} A trimmed copy of {@code str}.
*/
goog.string.trimLeft = function(str) {
// Since IE doesn't include non-breaking-space (0xa0) in their \s character
// class (as required by section 7.2 of the ECMAScript spec), we explicitly
// include it in the regexp to enforce consistent cross-browser behavior.
return str.replace(/^[\s\xa0]+/, '');
};
/**
* Trims whitespaces at the right end of a string.
* @param {string} str The string to right trim.
* @return {string} A trimmed copy of {@code str}.
*/
goog.string.trimRight = function(str) {
// Since IE doesn't include non-breaking-space (0xa0) in their \s character
// class (as required by section 7.2 of the ECMAScript spec), we explicitly
// include it in the regexp to enforce consistent cross-browser behavior.
return str.replace(/[\s\xa0]+$/, '');
};
/**
* A string comparator that ignores case.
* -1 = str1 less than str2
* 0 = str1 equals str2
* 1 = str1 greater than str2
*
* @param {string} str1 The string to compare.
* @param {string} str2 The string to compare {@code str1} to.
* @return {number} The comparator result, as described above.
*/
goog.string.caseInsensitiveCompare = function(str1, str2) {
var test1 = String(str1).toLowerCase();
var test2 = String(str2).toLowerCase();
if (test1 < test2) {
return -1;
} else if (test1 == test2) {
return 0;
} else {
return 1;
}
};
/**
* Compares two strings interpreting their numeric substrings as numbers.
*
* @param {string} str1 First string.
* @param {string} str2 Second string.
* @param {!RegExp} tokenizerRegExp Splits a string into substrings of
* non-negative integers, non-numeric characters and optionally fractional
* numbers starting with a decimal point.
* @return {number} Negative if str1 < str2, 0 is str1 == str2, positive if
* str1 > str2.
* @private
*/
goog.string.numberAwareCompare_ = function(str1, str2, tokenizerRegExp) {
if (str1 == str2) {
return 0;
}
if (!str1) {
return -1;
}
if (!str2) {
return 1;
}
// Using match to split the entire string ahead of time turns out to be faster
// for most inputs than using RegExp.exec or iterating over each character.
var tokens1 = str1.toLowerCase().match(tokenizerRegExp);
var tokens2 = str2.toLowerCase().match(tokenizerRegExp);
var count = Math.min(tokens1.length, tokens2.length);
for (var i = 0; i < count; i++) {
var a = tokens1[i];
var b = tokens2[i];
// Compare pairs of tokens, returning if one token sorts before the other.
if (a != b) {
// Only if both tokens are integers is a special comparison required.
// Decimal numbers are sorted as strings (e.g., '.09' < '.1').
var num1 = parseInt(a, 10);
if (!isNaN(num1)) {
var num2 = parseInt(b, 10);
if (!isNaN(num2) && num1 - num2) {
return num1 - num2;
}
}
return a < b ? -1 : 1;
}
}
// If one string is a substring of the other, the shorter string sorts first.
if (tokens1.length != tokens2.length) {
return tokens1.length - tokens2.length;
}
// The two strings must be equivalent except for case (perfect equality is
// tested at the head of the function.) Revert to default ASCII string
// comparison to stabilize the sort.
return str1 < str2 ? -1 : 1;
};
/**
* String comparison function that handles non-negative integer numbers in a
* way humans might expect. Using this function, the string 'File 2.jpg' sorts
* before 'File 10.jpg', and 'Version 1.9' before 'Version 1.10'. The comparison
* is mostly case-insensitive, though strings that are identical except for case
* are sorted with the upper-case strings before lower-case.
*
* This comparison function is up to 50x slower than either the default or the
* case-insensitive compare. It should not be used in time-critical code, but
* should be fast enough to sort several hundred short strings (like filenames)
* with a reasonable delay.
*
* @param {string} str1 The string to compare in a numerically sensitive way.
* @param {string} str2 The string to compare {@code str1} to.
* @return {number} less than 0 if str1 < str2, 0 if str1 == str2, greater than
* 0 if str1 > str2.
*/
goog.string.intAwareCompare = function(str1, str2) {
return goog.string.numberAwareCompare_(str1, str2, /\d+|\D+/g);
};
/**
* String comparison function that handles non-negative integer and fractional
* numbers in a way humans might expect. Using this function, the string
* 'File 2.jpg' sorts before 'File 10.jpg', and '3.14' before '3.2'. Equivalent
* to {@link goog.string.intAwareCompare} apart from the way how it interprets
* dots.
*
* @param {string} str1 The string to compare in a numerically sensitive way.
* @param {string} str2 The string to compare {@code str1} to.
* @return {number} less than 0 if str1 < str2, 0 if str1 == str2, greater than
* 0 if str1 > str2.
*/
goog.string.floatAwareCompare = function(str1, str2) {
return goog.string.numberAwareCompare_(str1, str2, /\d+|\.\d+|\D+/g);
};
/**
* Alias for {@link goog.string.floatAwareCompare}.
*
* @param {string} str1
* @param {string} str2
* @return {number}
*/
goog.string.numerateCompare = goog.string.floatAwareCompare;
/**
* URL-encodes a string
* @param {*} str The string to url-encode.
* @return {string} An encoded copy of {@code str} that is safe for urls.
* Note that '#', ':', and other characters used to delimit portions
* of URLs *will* be encoded.
*/
goog.string.urlEncode = function(str) {
return encodeURIComponent(String(str));
};
/**
* URL-decodes the string. We need to specially handle '+'s because
* the javascript library doesn't convert them to spaces.
* @param {string} str The string to url decode.
* @return {string} The decoded {@code str}.
*/
goog.string.urlDecode = function(str) {
return decodeURIComponent(str.replace(/\+/g, ' '));
};
/**
* Converts \n to <br>s or <br />s.
* @param {string} str The string in which to convert newlines.
* @param {boolean=} opt_xml Whether to use XML compatible tags.
* @return {string} A copy of {@code str} with converted newlines.
*/
goog.string.newLineToBr = function(str, opt_xml) {
return str.replace(/(\r\n|\r|\n)/g, opt_xml ? '<br />' : '<br>');
};
/**
* Escapes double quote '"' and single quote '\'' characters in addition to
* '&', '<', and '>' so that a string can be included in an HTML tag attribute
* value within double or single quotes.
*
* It should be noted that > doesn't need to be escaped for the HTML or XML to
* be valid, but it has been decided to escape it for consistency with other
* implementations.
*
* With goog.string.DETECT_DOUBLE_ESCAPING, this function escapes also the
* lowercase letter "e".
*
* NOTE(user):
* HtmlEscape is often called during the generation of large blocks of HTML.
* Using statics for the regular expressions and strings is an optimization
* that can more than half the amount of time IE spends in this function for
* large apps, since strings and regexes both contribute to GC allocations.
*
* Testing for the presence of a character before escaping increases the number
* of function calls, but actually provides a speed increase for the average
* case -- since the average case often doesn't require the escaping of all 4
* characters and indexOf() is much cheaper than replace().
* The worst case does suffer slightly from the additional calls, therefore the
* opt_isLikelyToContainHtmlChars option has been included for situations
* where all 4 HTML entities are very likely to be present and need escaping.
*
* Some benchmarks (times tended to fluctuate +-0.05ms):
* FireFox IE6
* (no chars / average (mix of cases) / all 4 chars)
* no checks 0.13 / 0.22 / 0.22 0.23 / 0.53 / 0.80
* indexOf 0.08 / 0.17 / 0.26 0.22 / 0.54 / 0.84
* indexOf + re test 0.07 / 0.17 / 0.28 0.19 / 0.50 / 0.85
*
* An additional advantage of checking if replace actually needs to be called
* is a reduction in the number of object allocations, so as the size of the
* application grows the difference between the various methods would increase.
*
* @param {string} str string to be escaped.
* @param {boolean=} opt_isLikelyToContainHtmlChars Don't perform a check to see
* if the character needs replacing - use this option if you expect each of
* the characters to appear often. Leave false if you expect few html
* characters to occur in your strings, such as if you are escaping HTML.
* @return {string} An escaped copy of {@code str}.
*/
goog.string.htmlEscape = function(str, opt_isLikelyToContainHtmlChars) {
if (opt_isLikelyToContainHtmlChars) {
str = str.replace(goog.string.AMP_RE_, '&amp;')
.replace(goog.string.LT_RE_, '&lt;')
.replace(goog.string.GT_RE_, '&gt;')
.replace(goog.string.QUOT_RE_, '&quot;')
.replace(goog.string.SINGLE_QUOTE_RE_, '&#39;')
.replace(goog.string.NULL_RE_, '&#0;');
if (goog.string.DETECT_DOUBLE_ESCAPING) {
str = str.replace(goog.string.E_RE_, '&#101;');
}
return str;
} else {
// quick test helps in the case when there are no chars to replace, in
// worst case this makes barely a difference to the time taken
if (!goog.string.ALL_RE_.test(str)) return str;
// str.indexOf is faster than regex.test in this case
if (str.indexOf('&') != -1) {
str = str.replace(goog.string.AMP_RE_, '&amp;');
}
if (str.indexOf('<') != -1) {
str = str.replace(goog.string.LT_RE_, '&lt;');
}
if (str.indexOf('>') != -1) {
str = str.replace(goog.string.GT_RE_, '&gt;');
}
if (str.indexOf('"') != -1) {
str = str.replace(goog.string.QUOT_RE_, '&quot;');
}
if (str.indexOf('\'') != -1) {
str = str.replace(goog.string.SINGLE_QUOTE_RE_, '&#39;');
}
if (str.indexOf('\x00') != -1) {
str = str.replace(goog.string.NULL_RE_, '&#0;');
}
if (goog.string.DETECT_DOUBLE_ESCAPING && str.indexOf('e') != -1) {
str = str.replace(goog.string.E_RE_, '&#101;');
}
return str;
}
};
/**
* Regular expression that matches an ampersand, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.AMP_RE_ = /&/g;
/**
* Regular expression that matches a less than sign, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.LT_RE_ = /</g;
/**
* Regular expression that matches a greater than sign, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.GT_RE_ = />/g;
/**
* Regular expression that matches a double quote, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.QUOT_RE_ = /"/g;
/**
* Regular expression that matches a single quote, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.SINGLE_QUOTE_RE_ = /'/g;
/**
* Regular expression that matches null character, for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.NULL_RE_ = /\x00/g;
/**
* Regular expression that matches a lowercase letter "e", for use in escaping.
* @const {!RegExp}
* @private
*/
goog.string.E_RE_ = /e/g;
/**
* Regular expression that matches any character that needs to be escaped.
* @const {!RegExp}
* @private
*/
goog.string.ALL_RE_ =
(goog.string.DETECT_DOUBLE_ESCAPING ? /[\x00&<>"'e]/ : /[\x00&<>"']/);
/**
* Unescapes an HTML string.
*
* @param {string} str The string to unescape.
* @return {string} An unescaped copy of {@code str}.
*/
goog.string.unescapeEntities = function(str) {
if (goog.string.contains(str, '&')) {
// We are careful not to use a DOM if we do not have one or we explicitly
// requested non-DOM html unescaping.
if (!goog.string.FORCE_NON_DOM_HTML_UNESCAPING &&
'document' in goog.global) {
return goog.string.unescapeEntitiesUsingDom_(str);
} else {
// Fall back on pure XML entities
return goog.string.unescapePureXmlEntities_(str);
}
}
return str;
};
/**
* Unescapes a HTML string using the provided document.
*
* @param {string} str The string to unescape.
* @param {!Document} document A document to use in escaping the string.
* @return {string} An unescaped copy of {@code str}.
*/
goog.string.unescapeEntitiesWithDocument = function(str, document) {
if (goog.string.contains(str, '&')) {
return goog.string.unescapeEntitiesUsingDom_(str, document);
}
return str;
};
/**
* Unescapes an HTML string using a DOM to resolve non-XML, non-numeric
* entities. This function is XSS-safe and whitespace-preserving.
* @private
* @param {string} str The string to unescape.
* @param {Document=} opt_document An optional document to use for creating
* elements. If this is not specified then the default window.document
* will be used.
* @return {string} The unescaped {@code str} string.
*/
goog.string.unescapeEntitiesUsingDom_ = function(str, opt_document) {
/** @type {!Object<string, string>} */
var seen = {'&amp;': '&', '&lt;': '<', '&gt;': '>', '&quot;': '"'};
var div;
if (opt_document) {
div = opt_document.createElement('div');
} else {
div = goog.global.document.createElement('div');
}
// Match as many valid entity characters as possible. If the actual entity
// happens to be shorter, it will still work as innerHTML will return the
// trailing characters unchanged. Since the entity characters do not include
// open angle bracket, there is no chance of XSS from the innerHTML use.
// Since no whitespace is passed to innerHTML, whitespace is preserved.
return str.replace(goog.string.HTML_ENTITY_PATTERN_, function(s, entity) {
// Check for cached entity.
var value = seen[s];
if (value) {
return value;
}
// Check for numeric entity.
if (entity.charAt(0) == '#') {
// Prefix with 0 so that hex entities (e.g. &#x10) parse as hex numbers.
var n = Number('0' + entity.substr(1));
if (!isNaN(n)) {
value = String.fromCharCode(n);
}
}
// Fall back to innerHTML otherwise.
if (!value) {
// Append a non-entity character to avoid a bug in Webkit that parses
// an invalid entity at the end of innerHTML text as the empty string.
div.innerHTML = s + ' ';
// Then remove the trailing character from the result.
value = div.firstChild.nodeValue.slice(0, -1);
}
// Cache and return.
return seen[s] = value;
});
};
/**
* Unescapes XML entities.
* @private
* @param {string} str The string to unescape.
* @return {string} An unescaped copy of {@code str}.
*/
goog.string.unescapePureXmlEntities_ = function(str) {
return str.replace(/&([^;]+);/g, function(s, entity) {
switch (entity) {
case 'amp':
return '&';
case 'lt':
return '<';
case 'gt':
return '>';
case 'quot':
return '"';
default:
if (entity.charAt(0) == '#') {
// Prefix with 0 so that hex entities (e.g. &#x10) parse as hex.
var n = Number('0' + entity.substr(1));
if (!isNaN(n)) {
return String.fromCharCode(n);
}
}
// For invalid entities we just return the entity
return s;
}
});
};
/**
* Regular expression that matches an HTML entity.
* See also HTML5: Tokenization / Tokenizing character references.
* @private
* @type {!RegExp}
*/
goog.string.HTML_ENTITY_PATTERN_ = /&([^;\s<&]+);?/g;
/**
* Do escaping of whitespace to preserve spatial formatting. We use character
* entity #160 to make it safer for xml.
* @param {string} str The string in which to escape whitespace.
* @param {boolean=} opt_xml Whether to use XML compatible tags.
* @return {string} An escaped copy of {@code str}.
*/
goog.string.whitespaceEscape = function(str, opt_xml) {
// This doesn't use goog.string.preserveSpaces for backwards compatibility.
return goog.string.newLineToBr(str.replace(/ /g, ' &#160;'), opt_xml);
};
/**
* Preserve spaces that would be otherwise collapsed in HTML by replacing them
* with non-breaking space Unicode characters.
* @param {string} str The string in which to preserve whitespace.
* @return {string} A copy of {@code str} with preserved whitespace.
*/
goog.string.preserveSpaces = function(str) {
return str.replace(/(^|[\n ]) /g, '$1' + goog.string.Unicode.NBSP);
};
/**
* Strip quote characters around a string. The second argument is a string of
* characters to treat as quotes. This can be a single character or a string of
* multiple character and in that case each of those are treated as possible
* quote characters. For example:
*
* <pre>
* goog.string.stripQuotes('"abc"', '"`') --> 'abc'
* goog.string.stripQuotes('`abc`', '"`') --> 'abc'
* </pre>
*
* @param {string} str The string to strip.
* @param {string} quoteChars The quote characters to strip.
* @return {string} A copy of {@code str} without the quotes.
*/
goog.string.stripQuotes = function(str, quoteChars) {
var length = quoteChars.length;
for (var i = 0; i < length; i++) {
var quoteChar = length == 1 ? quoteChars : quoteChars.charAt(i);
if (str.charAt(0) == quoteChar && str.charAt(str.length - 1) == quoteChar) {
return str.substring(1, str.length - 1);
}
}
return str;
};
/**
* Truncates a string to a certain length and adds '...' if necessary. The
* length also accounts for the ellipsis, so a maximum length of 10 and a string
* 'Hello World!' produces 'Hello W...'.
* @param {string} str The string to truncate.
* @param {number} chars Max number of characters.
* @param {boolean=} opt_protectEscapedCharacters Whether to protect escaped
* characters from being cut off in the middle.
* @return {string} The truncated {@code str} string.
*/
goog.string.truncate = function(str, chars, opt_protectEscapedCharacters) {
if (opt_protectEscapedCharacters) {
str = goog.string.unescapeEntities(str);
}
if (str.length > chars) {
str = str.substring(0, chars - 3) + '...';
}
if (opt_protectEscapedCharacters) {
str = goog.string.htmlEscape(str);
}
return str;
};
/**
* Truncate a string in the middle, adding "..." if necessary,
* and favoring the beginning of the string.
* @param {string} str The string to truncate the middle of.
* @param {number} chars Max number of characters.
* @param {boolean=} opt_protectEscapedCharacters Whether to protect escaped
* characters from being cutoff in the middle.
* @param {number=} opt_trailingChars Optional number of trailing characters to
* leave at the end of the string, instead of truncating as close to the
* middle as possible.
* @return {string} A truncated copy of {@code str}.
*/
goog.string.truncateMiddle = function(
str, chars, opt_protectEscapedCharacters, opt_trailingChars) {
if (opt_protectEscapedCharacters) {
str = goog.string.unescapeEntities(str);
}
if (opt_trailingChars && str.length > chars) {
if (opt_trailingChars > chars) {
opt_trailingChars = chars;
}
var endPoint = str.length - opt_trailingChars;
var startPoint = chars - opt_trailingChars;
str = str.substring(0, startPoint) + '...' + str.substring(endPoint);
} else if (str.length > chars) {
// Favor the beginning of the string:
var half = Math.floor(chars / 2);
var endPos = str.length - half;
half += chars % 2;
str = str.substring(0, half) + '...' + str.substring(endPos);
}
if (opt_protectEscapedCharacters) {
str = goog.string.htmlEscape(str);
}
return str;
};
/**
* Special chars that need to be escaped for goog.string.quote.
* @private {!Object<string, string>}
*/
goog.string.specialEscapeChars_ = {
'\0': '\\0',
'\b': '\\b',
'\f': '\\f',
'\n': '\\n',
'\r': '\\r',
'\t': '\\t',
'\x0B': '\\x0B', // '\v' is not supported in JScript
'"': '\\"',
'\\': '\\\\',
// To support the use case of embedding quoted strings inside of script
// tags, we have to make sure HTML comments and opening/closing script tags do
// not appear in the resulting string. The specific strings that must be
// escaped are documented at:
// http://www.w3.org/TR/html51/semantics.html#restrictions-for-contents-of-script-elements
'<': '\x3c'
};
/**
* Character mappings used internally for goog.string.escapeChar.
* @private {!Object<string, string>}
*/
goog.string.jsEscapeCache_ = {
'\'': '\\\''
};
/**
* Encloses a string in double quotes and escapes characters so that the
* string is a valid JS string. The resulting string is safe to embed in
* `<script>` tags as "<" is escaped.
* @param {string} s The string to quote.
* @return {string} A copy of {@code s} surrounded by double quotes.
*/
goog.string.quote = function(s) {
s = String(s);
var sb = ['"'];
for (var i = 0; i < s.length; i++) {
var ch = s.charAt(i);
var cc = ch.charCodeAt(0);
sb[i + 1] = goog.string.specialEscapeChars_[ch] ||
((cc > 31 && cc < 127) ? ch : goog.string.escapeChar(ch));
}
sb.push('"');
return sb.join('');
};
/**
* Takes a string and returns the escaped string for that character.
* @param {string} str The string to escape.
* @return {string} An escaped string representing {@code str}.
*/
goog.string.escapeString = function(str) {
var sb = [];
for (var i = 0; i < str.length; i++) {
sb[i] = goog.string.escapeChar(str.charAt(i));
}
return sb.join('');
};
/**
* Takes a character and returns the escaped string for that character. For
* example escapeChar(String.fromCharCode(15)) -> "\\x0E".
* @param {string} c The character to escape.
* @return {string} An escaped string representing {@code c}.
*/
goog.string.escapeChar = function(c) {
if (c in goog.string.jsEscapeCache_) {
return goog.string.jsEscapeCache_[c];
}
if (c in goog.string.specialEscapeChars_) {
return goog.string.jsEscapeCache_[c] = goog.string.specialEscapeChars_[c];
}
var rv = c;
var cc = c.charCodeAt(0);
if (cc > 31 && cc < 127) {
rv = c;
} else {
// tab is 9 but handled above
if (cc < 256) {
rv = '\\x';
if (cc < 16 || cc > 256) {
rv += '0';
}
} else {
rv = '\\u';
if (cc < 4096) { // \u1000
rv += '0';
}
}
rv += cc.toString(16).toUpperCase();
}
return goog.string.jsEscapeCache_[c] = rv;
};
/**
* Determines whether a string contains a substring.
* @param {string} str The string to search.
* @param {string} subString The substring to search for.
* @return {boolean} Whether {@code str} contains {@code subString}.
*/
goog.string.contains = function(str, subString) {
return str.indexOf(subString) != -1;
};
/**
* Determines whether a string contains a substring, ignoring case.
* @param {string} str The string to search.
* @param {string} subString The substring to search for.
* @return {boolean} Whether {@code str} contains {@code subString}.
*/
goog.string.caseInsensitiveContains = function(str, subString) {
return goog.string.contains(str.toLowerCase(), subString.toLowerCase());
};
/**
* Returns the non-overlapping occurrences of ss in s.
* If either s or ss evalutes to false, then returns zero.
* @param {string} s The string to look in.
* @param {string} ss The string to look for.
* @return {number} Number of occurrences of ss in s.
*/
goog.string.countOf = function(s, ss) {
return s && ss ? s.split(ss).length - 1 : 0;
};
/**
* Removes a substring of a specified length at a specific
* index in a string.
* @param {string} s The base string from which to remove.
* @param {number} index The index at which to remove the substring.
* @param {number} stringLength The length of the substring to remove.
* @return {string} A copy of {@code s} with the substring removed or the full
* string if nothing is removed or the input is invalid.
*/
goog.string.removeAt = function(s, index, stringLength) {
var resultStr = s;
// If the index is greater or equal to 0 then remove substring
if (index >= 0 && index < s.length && stringLength > 0) {
resultStr = s.substr(0, index) +
s.substr(index + stringLength, s.length - index - stringLength);
}
return resultStr;
};
/**
* Removes the first occurrence of a substring from a string.
* @param {string} s The base string from which to remove.
* @param {string} ss The string to remove.
* @return {string} A copy of {@code s} with {@code ss} removed or the full
* string if nothing is removed.
*/
goog.string.remove = function(s, ss) {
var re = new RegExp(goog.string.regExpEscape(ss), '');
return s.replace(re, '');
};
/**
* Removes all occurrences of a substring from a string.
* @param {string} s The base string from which to remove.
* @param {string} ss The string to remove.
* @return {string} A copy of {@code s} with {@code ss} removed or the full
* string if nothing is removed.
*/
goog.string.removeAll = function(s, ss) {
var re = new RegExp(goog.string.regExpEscape(ss), 'g');
return s.replace(re, '');
};
/**
* Escapes characters in the string that are not safe to use in a RegExp.
* @param {*} s The string to escape. If not a string, it will be casted
* to one.
* @return {string} A RegExp safe, escaped copy of {@code s}.
*/
goog.string.regExpEscape = function(s) {
return String(s)
.replace(/([-()\[\]{}+?*.$\^|,:#<!\\])/g, '\\$1')
.replace(/\x08/g, '\\x08');
};
/**
* Repeats a string n times.
* @param {string} string The string to repeat.
* @param {number} length The number of times to repeat.
* @return {string} A string containing {@code length} repetitions of
* {@code string}.
*/
goog.string.repeat = (String.prototype.repeat) ? function(string, length) {
// The native method is over 100 times faster than the alternative.
return string.repeat(length);
} : function(string, length) {
return new Array(length + 1).join(string);
};
/**
* Pads number to given length and optionally rounds it to a given precision.
* For example:
* <pre>padNumber(1.25, 2, 3) -> '01.250'
* padNumber(1.25, 2) -> '01.25'
* padNumber(1.25, 2, 1) -> '01.3'
* padNumber(1.25, 0) -> '1.25'</pre>
*
* @param {number} num The number to pad.
* @param {number} length The desired length.
* @param {number=} opt_precision The desired precision.
* @return {string} {@code num} as a string with the given options.
*/
goog.string.padNumber = function(num, length, opt_precision) {
var s = goog.isDef(opt_precision) ? num.toFixed(opt_precision) : String(num);
var index = s.indexOf('.');
if (index == -1) {
index = s.length;
}
return goog.string.repeat('0', Math.max(0, length - index)) + s;
};
/**
* Returns a string representation of the given object, with
* null and undefined being returned as the empty string.
*
* @param {*} obj The object to convert.
* @return {string} A string representation of the {@code obj}.
*/
goog.string.makeSafe = function(obj) {
return obj == null ? '' : String(obj);
};
/**
* Concatenates string expressions. This is useful
* since some browsers are very inefficient when it comes to using plus to
* concat strings. Be careful when using null and undefined here since
* these will not be included in the result. If you need to represent these
* be sure to cast the argument to a String first.
* For example:
* <pre>buildString('a', 'b', 'c', 'd') -> 'abcd'
* buildString(null, undefined) -> ''
* </pre>
* @param {...*} var_args A list of strings to concatenate. If not a string,
* it will be casted to one.
* @return {string} The concatenation of {@code var_args}.
*/
goog.string.buildString = function(var_args) {
return Array.prototype.join.call(arguments, '');
};
/**
* Returns a string with at least 64-bits of randomness.
*
* Doesn't trust Javascript's random function entirely. Uses a combination of
* random and current timestamp, and then encodes the string in base-36 to
* make it shorter.
*
* @return {string} A random string, e.g. sn1s7vb4gcic.
*/
goog.string.getRandomString = function() {
var x = 2147483648;
return Math.floor(Math.random() * x).toString(36) +
Math.abs(Math.floor(Math.random() * x) ^ goog.now()).toString(36);
};
/**
* Compares two version numbers.
*
* @param {string|number} version1 Version of first item.
* @param {string|number} version2 Version of second item.
*
* @return {number} 1 if {@code version1} is higher.
* 0 if arguments are equal.
* -1 if {@code version2} is higher.
*/
goog.string.compareVersions = function(version1, version2) {
var order = 0;
// Trim leading and trailing whitespace and split the versions into
// subversions.
var v1Subs = goog.string.trim(String(version1)).split('.');
var v2Subs = goog.string.trim(String(version2)).split('.');
var subCount = Math.max(v1Subs.length, v2Subs.length);
// Iterate over the subversions, as long as they appear to be equivalent.
for (var subIdx = 0; order == 0 && subIdx < subCount; subIdx++) {
var v1Sub = v1Subs[subIdx] || '';
var v2Sub = v2Subs[subIdx] || '';
// Split the subversions into pairs of numbers and qualifiers (like 'b').
// Two different RegExp objects are needed because they are both using
// the 'g' flag.
var v1CompParser = new RegExp('(\\d*)(\\D*)', 'g');
var v2CompParser = new RegExp('(\\d*)(\\D*)', 'g');
do {
var v1Comp = v1CompParser.exec(v1Sub) || ['', '', ''];
var v2Comp = v2CompParser.exec(v2Sub) || ['', '', ''];
// Break if there are no more matches.
if (v1Comp[0].length == 0 && v2Comp[0].length == 0) {
break;
}
// Parse the numeric part of the subversion. A missing number is
// equivalent to 0.
var v1CompNum = v1Comp[1].length == 0 ? 0 : parseInt(v1Comp[1], 10);
var v2CompNum = v2Comp[1].length == 0 ? 0 : parseInt(v2Comp[1], 10);
// Compare the subversion components. The number has the highest
// precedence. Next, if the numbers are equal, a subversion without any
// qualifier is always higher than a subversion with any qualifier. Next,
// the qualifiers are compared as strings.
order = goog.string.compareElements_(v1CompNum, v2CompNum) ||
goog.string.compareElements_(
v1Comp[2].length == 0, v2Comp[2].length == 0) ||
goog.string.compareElements_(v1Comp[2], v2Comp[2]);
// Stop as soon as an inequality is discovered.
} while (order == 0);
}
return order;
};
/**
* Compares elements of a version number.
*
* @param {string|number|boolean} left An element from a version number.
* @param {string|number|boolean} right An element from a version number.
*
* @return {number} 1 if {@code left} is higher.
* 0 if arguments are equal.
* -1 if {@code right} is higher.
* @private
*/
goog.string.compareElements_ = function(left, right) {
if (left < right) {
return -1;
} else if (left > right) {
return 1;
}
return 0;
};
/**
* String hash function similar to java.lang.String.hashCode().
* The hash code for a string is computed as
* s[0] * 31 ^ (n - 1) + s[1] * 31 ^ (n - 2) + ... + s[n - 1],
* where s[i] is the ith character of the string and n is the length of
* the string. We mod the result to make it between 0 (inclusive) and 2^32
* (exclusive).
* @param {string} str A string.
* @return {number} Hash value for {@code str}, between 0 (inclusive) and 2^32
* (exclusive). The empty string returns 0.
*/
goog.string.hashCode = function(str) {
var result = 0;
for (var i = 0; i < str.length; ++i) {
// Normalize to 4 byte range, 0 ... 2^32.
result = (31 * result + str.charCodeAt(i)) >>> 0;
}
return result;
};
/**
* The most recent unique ID. |0 is equivalent to Math.floor in this case.
* @type {number}
* @private
*/
goog.string.uniqueStringCounter_ = Math.random() * 0x80000000 | 0;
/**
* Generates and returns a string which is unique in the current document.
* This is useful, for example, to create unique IDs for DOM elements.
* @return {string} A unique id.
*/
goog.string.createUniqueString = function() {
return 'goog_' + goog.string.uniqueStringCounter_++;
};
/**
* Converts the supplied string to a number, which may be Infinity or NaN.
* This function strips whitespace: (toNumber(' 123') === 123)
* This function accepts scientific notation: (toNumber('1e1') === 10)
*
* This is better than Javascript's built-in conversions because, sadly:
* (Number(' ') === 0) and (parseFloat('123a') === 123)
*
* @param {string} str The string to convert.
* @return {number} The number the supplied string represents, or NaN.
*/
goog.string.toNumber = function(str) {
var num = Number(str);
if (num == 0 && goog.string.isEmptyOrWhitespace(str)) {
return NaN;
}
return num;
};
/**
* Returns whether the given string is lower camel case (e.g. "isFooBar").
*
* Note that this assumes the string is entirely letters.
* @see http://en.wikipedia.org/wiki/CamelCase#Variations_and_synonyms
*
* @param {string} str String to test.
* @return {boolean} Whether the string is lower camel case.
*/
goog.string.isLowerCamelCase = function(str) {
return /^[a-z]+([A-Z][a-z]*)*$/.test(str);
};
/**
* Returns whether the given string is upper camel case (e.g. "FooBarBaz").
*
* Note that this assumes the string is entirely letters.
* @see http://en.wikipedia.org/wiki/CamelCase#Variations_and_synonyms
*
* @param {string} str String to test.
* @return {boolean} Whether the string is upper camel case.
*/
goog.string.isUpperCamelCase = function(str) {
return /^([A-Z][a-z]*)+$/.test(str);
};
/**
* Converts a string from selector-case to camelCase (e.g. from
* "multi-part-string" to "multiPartString"), useful for converting
* CSS selectors and HTML dataset keys to their equivalent JS properties.
* @param {string} str The string in selector-case form.
* @return {string} The string in camelCase form.
*/
goog.string.toCamelCase = function(str) {
return String(str).replace(
/\-([a-z])/g, function(all, match) { return match.toUpperCase(); });
};
/**
* Converts a string from camelCase to selector-case (e.g. from
* "multiPartString" to "multi-part-string"), useful for converting JS
* style and dataset properties to equivalent CSS selectors and HTML keys.
* @param {string} str The string in camelCase form.
* @return {string} The string in selector-case form.
*/
goog.string.toSelectorCase = function(str) {
return String(str).replace(/([A-Z])/g, '-$1').toLowerCase();
};
/**
* Converts a string into TitleCase. First character of the string is always
* capitalized in addition to the first letter of every subsequent word.
* Words are delimited by one or more whitespaces by default. Custom delimiters
* can optionally be specified to replace the default, which doesn't preserve
* whitespace delimiters and instead must be explicitly included if needed.
*
* Default delimiter => " ":
* goog.string.toTitleCase('oneTwoThree') => 'OneTwoThree'
* goog.string.toTitleCase('one two three') => 'One Two Three'
* goog.string.toTitleCase(' one two ') => ' One Two '
* goog.string.toTitleCase('one_two_three') => 'One_two_three'
* goog.string.toTitleCase('one-two-three') => 'One-two-three'
*
* Custom delimiter => "_-.":
* goog.string.toTitleCase('oneTwoThree', '_-.') => 'OneTwoThree'
* goog.string.toTitleCase('one two three', '_-.') => 'One two three'
* goog.string.toTitleCase(' one two ', '_-.') => ' one two '
* goog.string.toTitleCase('one_two_three', '_-.') => 'One_Two_Three'
* goog.string.toTitleCase('one-two-three', '_-.') => 'One-Two-Three'
* goog.string.toTitleCase('one...two...three', '_-.') => 'One...Two...Three'
* goog.string.toTitleCase('one. two. three', '_-.') => 'One. two. three'
* goog.string.toTitleCase('one-two.three', '_-.') => 'One-Two.Three'
*
* @param {string} str String value in camelCase form.
* @param {string=} opt_delimiters Custom delimiter character set used to
* distinguish words in the string value. Each character represents a
* single delimiter. When provided, default whitespace delimiter is
* overridden and must be explicitly included if needed.
* @return {string} String value in TitleCase form.
*/
goog.string.toTitleCase = function(str, opt_delimiters) {
var delimiters = goog.isString(opt_delimiters) ?
goog.string.regExpEscape(opt_delimiters) :
'\\s';
// For IE8, we need to prevent using an empty character set. Otherwise,
// incorrect matching will occur.
delimiters = delimiters ? '|[' + delimiters + ']+' : '';
var regexp = new RegExp('(^' + delimiters + ')([a-z])', 'g');
return str.replace(
regexp, function(all, p1, p2) { return p1 + p2.toUpperCase(); });
};
/**
* Capitalizes a string, i.e. converts the first letter to uppercase
* and all other letters to lowercase, e.g.:
*
* goog.string.capitalize('one') => 'One'
* goog.string.capitalize('ONE') => 'One'
* goog.string.capitalize('one two') => 'One two'
*
* Note that this function does not trim initial whitespace.
*
* @param {string} str String value to capitalize.
* @return {string} String value with first letter in uppercase.
*/
goog.string.capitalize = function(str) {
return String(str.charAt(0)).toUpperCase() +
String(str.substr(1)).toLowerCase();
};
/**
* Parse a string in decimal or hexidecimal ('0xFFFF') form.
*
* To parse a particular radix, please use parseInt(string, radix) directly. See
* https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/parseInt
*
* This is a wrapper for the built-in parseInt function that will only parse
* numbers as base 10 or base 16. Some JS implementations assume strings
* starting with "0" are intended to be octal. ES3 allowed but discouraged
* this behavior. ES5 forbids it. This function emulates the ES5 behavior.
*
* For more information, see Mozilla JS Reference: http://goo.gl/8RiFj
*
* @param {string|number|null|undefined} value The value to be parsed.
* @return {number} The number, parsed. If the string failed to parse, this
* will be NaN.
*/
goog.string.parseInt = function(value) {
// Force finite numbers to strings.
if (isFinite(value)) {
value = String(value);
}
if (goog.isString(value)) {
// If the string starts with '0x' or '-0x', parse as hex.
return /^\s*-?0x/i.test(value) ? parseInt(value, 16) : parseInt(value, 10);
}
return NaN;
};
/**
* Splits a string on a separator a limited number of times.
*
* This implementation is more similar to Python or Java, where the limit
* parameter specifies the maximum number of splits rather than truncating
* the number of results.
*
* See http://docs.python.org/2/library/stdtypes.html#str.split
* See JavaDoc: http://goo.gl/F2AsY
* See Mozilla reference: http://goo.gl/dZdZs
*
* @param {string} str String to split.
* @param {string} separator The separator.
* @param {number} limit The limit to the number of splits. The resulting array
* will have a maximum length of limit+1. Negative numbers are the same
* as zero.
* @return {!Array<string>} The string, split.
*/
goog.string.splitLimit = function(str, separator, limit) {
var parts = str.split(separator);
var returnVal = [];
// Only continue doing this while we haven't hit the limit and we have
// parts left.
while (limit > 0 && parts.length) {
returnVal.push(parts.shift());
limit--;
}
// If there are remaining parts, append them to the end.
if (parts.length) {
returnVal.push(parts.join(separator));
}
return returnVal;
};
/**
* Finds the characters to the right of the last instance of any separator
*
* This function is similar to goog.string.path.baseName, except it can take a
* list of characters to split the string on. It will return the rightmost
* grouping of characters to the right of any separator as a left-to-right
* oriented string.
*
* @see goog.string.path.baseName
* @param {string} str The string
* @param {string|!Array<string>} separators A list of separator characters
* @return {string} The last part of the string with respect to the separators
*/
goog.string.lastComponent = function(str, separators) {
if (!separators) {
return str;
} else if (typeof separators == 'string') {
separators = [separators];
}
var lastSeparatorIndex = -1;
for (var i = 0; i < separators.length; i++) {
if (separators[i] == '') {
continue;
}
var currentSeparatorIndex = str.lastIndexOf(separators[i]);
if (currentSeparatorIndex > lastSeparatorIndex) {
lastSeparatorIndex = currentSeparatorIndex;
}
}
if (lastSeparatorIndex == -1) {
return str;
}
return str.slice(lastSeparatorIndex + 1);
};
/**
* Computes the Levenshtein edit distance between two strings.
* @param {string} a
* @param {string} b
* @return {number} The edit distance between the two strings.
*/
goog.string.editDistance = function(a, b) {
var v0 = [];
var v1 = [];
if (a == b) {
return 0;
}
if (!a.length || !b.length) {
return Math.max(a.length, b.length);
}
for (var i = 0; i < b.length + 1; i++) {
v0[i] = i;
}
for (var i = 0; i < a.length; i++) {
v1[0] = i + 1;
for (var j = 0; j < b.length; j++) {
var cost = Number(a[i] != b[j]);
// Cost for the substring is the minimum of adding one character, removing
// one character, or a swap.
v1[j + 1] = Math.min(v1[j] + 1, v0[j + 1] + 1, v0[j] + cost);
}
for (var j = 0; j < v0.length; j++) {
v0[j] = v1[j];
}
}
return v1[b.length];
};
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