mediocre-blog/assets/viz/1/goog/reflect/reflect.js
2018-11-12 15:29:55 -05:00

139 lines
4.5 KiB
JavaScript

// Copyright 2009 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 Useful compiler idioms.
*
* @author johnlenz@google.com (John Lenz)
*/
goog.provide('goog.reflect');
/**
* Syntax for object literal casts.
* @see http://go/jscompiler-renaming
* @see https://goo.gl/CRs09P
*
* Use this if you have an object literal whose keys need to have the same names
* as the properties of some class even after they are renamed by the compiler.
*
* @param {!Function} type Type to cast to.
* @param {Object} object Object literal to cast.
* @return {Object} The object literal.
*/
goog.reflect.object = function(type, object) {
return object;
};
/**
* Syntax for renaming property strings.
* @see http://go/jscompiler-renaming
* @see https://goo.gl/CRs09P
*
* Use this if you have an need to access a property as a string, but want
* to also have the property renamed by the compiler. In contrast to
* goog.reflect.object, this method takes an instance of an object.
*
* Properties must be simple names (not qualified names).
*
* @param {string} prop Name of the property
* @param {!Object} object Instance of the object whose type will be used
* for renaming
* @return {string} The renamed property.
*/
goog.reflect.objectProperty = function(prop, object) {
return prop;
};
/**
* To assert to the compiler that an operation is needed when it would
* otherwise be stripped. For example:
* <code>
* // Force a layout
* goog.reflect.sinkValue(dialog.offsetHeight);
* </code>
* @param {T} x
* @return {T}
* @template T
*/
goog.reflect.sinkValue = function(x) {
goog.reflect.sinkValue[' '](x);
return x;
};
/**
* The compiler should optimize this function away iff no one ever uses
* goog.reflect.sinkValue.
*/
goog.reflect.sinkValue[' '] = goog.nullFunction;
/**
* Check if a property can be accessed without throwing an exception.
* @param {Object} obj The owner of the property.
* @param {string} prop The property name.
* @return {boolean} Whether the property is accessible. Will also return true
* if obj is null.
*/
goog.reflect.canAccessProperty = function(obj, prop) {
/** @preserveTry */
try {
goog.reflect.sinkValue(obj[prop]);
return true;
} catch (e) {
}
return false;
};
/**
* Retrieves a value from a cache given a key. The compiler provides special
* consideration for this call such that it is generally considered side-effect
* free. However, if the {@code opt_keyFn} or {@code valueFn} have side-effects
* then the entire call is considered to have side-effects.
*
* Conventionally storing the value on the cache would be considered a
* side-effect and preclude unused calls from being pruned, ie. even if
* the value was never used, it would still always be stored in the cache.
*
* Providing a side-effect free {@code valueFn} and {@code opt_keyFn}
* allows unused calls to {@code goog.cache} to be pruned.
*
* @param {!Object<K, V>} cacheObj The object that contains the cached values.
* @param {?} key The key to lookup in the cache. If it is not string or number
* then a {@code opt_keyFn} should be provided. The key is also used as the
* parameter to the {@code valueFn}.
* @param {!function(?):V} valueFn The value provider to use to calculate the
* value to store in the cache. This function should be side-effect free
* to take advantage of the optimization.
* @param {function(?):K=} opt_keyFn The key provider to determine the cache
* map key. This should be used if the given key is not a string or number.
* If not provided then the given key is used. This function should be
* side-effect free to take advantage of the optimization.
* @return {V} The cached or calculated value.
* @template K
* @template V
*/
goog.reflect.cache = function(cacheObj, key, valueFn, opt_keyFn) {
var storedKey = opt_keyFn ? opt_keyFn(key) : key;
if (Object.prototype.hasOwnProperty.call(cacheObj, storedKey)) {
return cacheObj[storedKey];
}
return (cacheObj[storedKey] = valueFn(key));
};