lib/goog/json/json.js

1// Copyright 2006 The Closure Library Authors. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS-IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15/**
16 * @fileoverview JSON utility functions.
17 * @author arv@google.com (Erik Arvidsson)
18 */
19
20
21goog.provide('goog.json');
22goog.provide('goog.json.Serializer');
23
24
25/**
26 * Tests if a string is an invalid JSON string. This only ensures that we are
27 * not using any invalid characters
28 * @param {string} s The string to test.
29 * @return {boolean} True if the input is a valid JSON string.
30 * @private
31 */
32goog.json.isValid_ = function(s) {
33 // All empty whitespace is not valid.
34 if (/^\s*$/.test(s)) {
35 return false;
36 }
37
38 // This is taken from http://www.json.org/json2.js which is released to the
39 // public domain.
40 // Changes: We dissallow \u2028 Line separator and \u2029 Paragraph separator
41 // inside strings. We also treat \u2028 and \u2029 as whitespace which they
42 // are in the RFC but IE and Safari does not match \s to these so we need to
43 // include them in the reg exps in all places where whitespace is allowed.
44 // We allowed \x7f inside strings because some tools don't escape it,
45 // e.g. http://www.json.org/java/org/json/JSONObject.java
46
47 // Parsing happens in three stages. In the first stage, we run the text
48 // against regular expressions that look for non-JSON patterns. We are
49 // especially concerned with '()' and 'new' because they can cause invocation,
50 // and '=' because it can cause mutation. But just to be safe, we want to
51 // reject all unexpected forms.
52
53 // We split the first stage into 4 regexp operations in order to work around
54 // crippling inefficiencies in IE's and Safari's regexp engines. First we
55 // replace all backslash pairs with '@' (a non-JSON character). Second, we
56 // replace all simple value tokens with ']' characters. Third, we delete all
57 // open brackets that follow a colon or comma or that begin the text. Finally,
58 // we look to see that the remaining characters are only whitespace or ']' or
59 // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
60
61 // Don't make these static since they have the global flag.
62 var backslashesRe = /\\["\\\/bfnrtu]/g;
63 var simpleValuesRe =
64 /"[^"\\\n\r\u2028\u2029\x00-\x08\x0a-\x1f]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g;
65 var openBracketsRe = /(?:^|:|,)(?:[\s\u2028\u2029]*\[)+/g;
66 var remainderRe = /^[\],:{}\s\u2028\u2029]*$/;
67
68 return remainderRe.test(s.replace(backslashesRe, '@').
69 replace(simpleValuesRe, ']').
70 replace(openBracketsRe, ''));
71};
72
73
74/**
75 * Parses a JSON string and returns the result. This throws an exception if
76 * the string is an invalid JSON string.
77 *
78 * Note that this is very slow on large strings. If you trust the source of
79 * the string then you should use unsafeParse instead.
80 *
81 * @param {*} s The JSON string to parse.
82 * @return {Object} The object generated from the JSON string.
83 */
84goog.json.parse = function(s) {
85 var o = String(s);
86 if (goog.json.isValid_(o)) {
87 /** @preserveTry */
88 try {
89 return /** @type {Object} */ (eval('(' + o + ')'));
90 } catch (ex) {
91 }
92 }
93 throw Error('Invalid JSON string: ' + o);
94};
95
96
97/**
98 * Parses a JSON string and returns the result. This uses eval so it is open
99 * to security issues and it should only be used if you trust the source.
100 *
101 * @param {string} s The JSON string to parse.
102 * @return {Object} The object generated from the JSON string.
103 */
104goog.json.unsafeParse = function(s) {
105 return /** @type {Object} */ (eval('(' + s + ')'));
106};
107
108
109/**
110 * JSON replacer, as defined in Section 15.12.3 of the ES5 spec.
111 *
112 * TODO(nicksantos): Array should also be a valid replacer.
113 *
114 * @typedef {function(this:Object, string, *): *}
115 */
116goog.json.Replacer;
117
118
119/**
120 * JSON reviver, as defined in Section 15.12.2 of the ES5 spec.
121 *
122 * @typedef {function(this:Object, string, *): *}
123 */
124goog.json.Reviver;
125
126
127/**
128 * Serializes an object or a value to a JSON string.
129 *
130 * @param {*} object The object to serialize.
131 * @param {?goog.json.Replacer=} opt_replacer A replacer function
132 * called for each (key, value) pair that determines how the value
133 * should be serialized. By defult, this just returns the value
134 * and allows default serialization to kick in.
135 * @throws Error if there are loops in the object graph.
136 * @return {string} A JSON string representation of the input.
137 */
138goog.json.serialize = function(object, opt_replacer) {
139 // NOTE(nicksantos): Currently, we never use JSON.stringify.
140 //
141 // The last time I evaluated this, JSON.stringify had subtle bugs and behavior
142 // differences on all browsers, and the performance win was not large enough
143 // to justify all the issues. This may change in the future as browser
144 // implementations get better.
145 //
146 // assertSerialize in json_test contains if branches for the cases
147 // that fail.
148 return new goog.json.Serializer(opt_replacer).serialize(object);
149};
150
151
152
153/**
154 * Class that is used to serialize JSON objects to a string.
155 * @param {?goog.json.Replacer=} opt_replacer Replacer.
156 * @constructor
157 */
158goog.json.Serializer = function(opt_replacer) {
159 /**
160 * @type {goog.json.Replacer|null|undefined}
161 * @private
162 */
163 this.replacer_ = opt_replacer;
164};
165
166
167/**
168 * Serializes an object or a value to a JSON string.
169 *
170 * @param {*} object The object to serialize.
171 * @throws Error if there are loops in the object graph.
172 * @return {string} A JSON string representation of the input.
173 */
174goog.json.Serializer.prototype.serialize = function(object) {
175 var sb = [];
176 this.serialize_(object, sb);
177 return sb.join('');
178};
179
180
181/**
182 * Serializes a generic value to a JSON string
183 * @private
184 * @param {*} object The object to serialize.
185 * @param {Array} sb Array used as a string builder.
186 * @throws Error if there are loops in the object graph.
187 */
188goog.json.Serializer.prototype.serialize_ = function(object, sb) {
189 switch (typeof object) {
190 case 'string':
191 this.serializeString_(/** @type {string} */ (object), sb);
192 break;
193 case 'number':
194 this.serializeNumber_(/** @type {number} */ (object), sb);
195 break;
196 case 'boolean':
197 sb.push(object);
198 break;
199 case 'undefined':
200 sb.push('null');
201 break;
202 case 'object':
203 if (object == null) {
204 sb.push('null');
205 break;
206 }
207 if (goog.isArray(object)) {
208 this.serializeArray(/** @type {!Array} */ (object), sb);
209 break;
210 }
211 // should we allow new String, new Number and new Boolean to be treated
212 // as string, number and boolean? Most implementations do not and the
213 // need is not very big
214 this.serializeObject_(/** @type {Object} */ (object), sb);
215 break;
216 case 'function':
217 // Skip functions.
218 // TODO(user) Should we return something here?
219 break;
220 default:
221 throw Error('Unknown type: ' + typeof object);
222 }
223};
224
225
226/**
227 * Character mappings used internally for goog.string.quote
228 * @private
229 * @type {Object}
230 */
231goog.json.Serializer.charToJsonCharCache_ = {
232 '\"': '\\"',
233 '\\': '\\\\',
234 '/': '\\/',
235 '\b': '\\b',
236 '\f': '\\f',
237 '\n': '\\n',
238 '\r': '\\r',
239 '\t': '\\t',
240
241 '\x0B': '\\u000b' // '\v' is not supported in JScript
242};
243
244
245/**
246 * Regular expression used to match characters that need to be replaced.
247 * The S60 browser has a bug where unicode characters are not matched by
248 * regular expressions. The condition below detects such behaviour and
249 * adjusts the regular expression accordingly.
250 * @private
251 * @type {RegExp}
252 */
253goog.json.Serializer.charsToReplace_ = /\uffff/.test('\uffff') ?
254 /[\\\"\x00-\x1f\x7f-\uffff]/g : /[\\\"\x00-\x1f\x7f-\xff]/g;
255
256
257/**
258 * Serializes a string to a JSON string
259 * @private
260 * @param {string} s The string to serialize.
261 * @param {Array} sb Array used as a string builder.
262 */
263goog.json.Serializer.prototype.serializeString_ = function(s, sb) {
264 // The official JSON implementation does not work with international
265 // characters.
266 sb.push('"', s.replace(goog.json.Serializer.charsToReplace_, function(c) {
267 // caching the result improves performance by a factor 2-3
268 if (c in goog.json.Serializer.charToJsonCharCache_) {
269 return goog.json.Serializer.charToJsonCharCache_[c];
270 }
271
272 var cc = c.charCodeAt(0);
273 var rv = '\\u';
274 if (cc < 16) {
275 rv += '000';
276 } else if (cc < 256) {
277 rv += '00';
278 } else if (cc < 4096) { // \u1000
279 rv += '0';
280 }
281 return goog.json.Serializer.charToJsonCharCache_[c] = rv + cc.toString(16);
282 }), '"');
283};
284
285
286/**
287 * Serializes a number to a JSON string
288 * @private
289 * @param {number} n The number to serialize.
290 * @param {Array} sb Array used as a string builder.
291 */
292goog.json.Serializer.prototype.serializeNumber_ = function(n, sb) {
293 sb.push(isFinite(n) && !isNaN(n) ? n : 'null');
294};
295
296
297/**
298 * Serializes an array to a JSON string
299 * @param {Array} arr The array to serialize.
300 * @param {Array} sb Array used as a string builder.
301 * @protected
302 */
303goog.json.Serializer.prototype.serializeArray = function(arr, sb) {
304 var l = arr.length;
305 sb.push('[');
306 var sep = '';
307 for (var i = 0; i < l; i++) {
308 sb.push(sep);
309
310 var value = arr[i];
311 this.serialize_(
312 this.replacer_ ? this.replacer_.call(arr, String(i), value) : value,
313 sb);
314
315 sep = ',';
316 }
317 sb.push(']');
318};
319
320
321/**
322 * Serializes an object to a JSON string
323 * @private
324 * @param {Object} obj The object to serialize.
325 * @param {Array} sb Array used as a string builder.
326 */
327goog.json.Serializer.prototype.serializeObject_ = function(obj, sb) {
328 sb.push('{');
329 var sep = '';
330 for (var key in obj) {
331 if (Object.prototype.hasOwnProperty.call(obj, key)) {
332 var value = obj[key];
333 // Skip functions.
334 // TODO(ptucker) Should we return something for function properties?
335 if (typeof value != 'function') {
336 sb.push(sep);
337 this.serializeString_(key, sb);
338 sb.push(':');
339
340 this.serialize_(
341 this.replacer_ ? this.replacer_.call(obj, key, value) : value,
342 sb);
343
344 sep = ',';
345 }
346 }
347 }
348 sb.push('}');
349};