1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
// 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));
};
|
