json.js

  1 /*
  2     json.js
  3     2007-08-05
  4 
  5     Public Domain
  6 
  7     This file adds these methods to JavaScript:
  8 
  9         array.toJSONString()
 10         boolean.toJSONString()
 11         date.toJSONString()
 12         number.toJSONString()
 13         object.toJSONString()
 14         string.toJSONString()
 15             These methods produce a JSON text from a JavaScript value.
 16             It must not contain any cyclical references. Illegal values
 17             will be excluded.
 18 
 19             The default conversion for dates is to an ISO string. You can
 20             add a toJSONString method to any date object to get a different
 21             representation.
 22 
 23         string.parseJSON(filter)
 24             This method parses a JSON text to produce an object or
 25             array. It can throw a SyntaxError exception.
 26 
 27             The optional filter parameter is a function which can filter and
 28             transform the results. It receives each of the keys and values, and
 29             its return value is used instead of the original value. If it
 30             returns what it received, then structure is not modified. If it
 31             returns undefined then the member is deleted.
 32 
 33             Example:
 34 
 35             // Parse the text. If a key contains the string ‘date‘ then
 36             // convert the value to a date.
 37 
 38             myData = text.parseJSON(function (key, value) {
 39                 return key.indexOf(‘date‘) >= 0 ? new Date(value) : value;
 40             });
 41 
 42     It is expected that these methods will formally become part of the
 43     JavaScript Programming Language in the Fourth Edition of the
 44     ECMAScript standard in 2008.
 45 
 46     This file will break programs with improper for..in loops. See
 47     http://yuiblog.com/blog/2006/09/26/for-in-intrigue/
 48 
 49     This is a reference implementation. You are free to copy, modify, or
 50     redistribute.
 51 
 52     Use your own copy. It is extremely unwise to load untrusted third party
 53     code into your pages.
 54 */
 55 
 56 /*jslint evil: true */
 57 
 58 // Augment the basic prototypes if they have not already been augmented.
 59 
 60 if (!Object.prototype.toJSONString) {
 61 
 62     Array.prototype.toJSONString = function () {
 63         var a = [],     // The array holding the partial texts.
 64             i,          // Loop counter.
 65             l = this.length,
 66             v;          // The value to be stringified.
 67 
 68 
 69 // For each value in this array...
 70 
 71         for (i = 0; i < l; i += 1) {
 72             v = this[i];
 73             switch (typeof v) {
 74             case ‘object‘:
 75 
 76 // Serialize a JavaScript object value. Ignore objects thats lack the
 77 // toJSONString method. Due to a specification error in ECMAScript,
 78 // typeof null is ‘object‘, so watch out for that case.
 79 
 80                 if (v) {
 81                     if (typeof v.toJSONString === ‘function‘) {
 82                         a.push(v.toJSONString());
 83                     }
 84                 } else {
 85                     a.push(‘null‘);
 86                 }
 87                 break;
 88 
 89             case ‘string‘:
 90             case ‘number‘:
 91             case ‘boolean‘:
 92                 a.push(v.toJSONString());
 93 
 94 // Values without a JSON representation are ignored.
 95 
 96             }
 97         }
 98 
 99 // Join all of the member texts together and wrap them in brackets.
100 
101         return ‘[‘ + a.join(‘,‘) + ‘]‘;
102     };
103 
104 
105     Boolean.prototype.toJSONString = function () {
106         return String(this);
107     };
108 
109 
110     Date.prototype.toJSONString = function () {
111 
112 // Eventually, this method will be based on the date.toISOString method.
113 
114         function f(n) {
115 
116 // Format integers to have at least two digits.
117 
118             return n < 10 ? ‘0‘ + n : n;
119         }
120 
121         return ‘"‘ + this.getUTCFullYear() + ‘-‘ +
122                 f(this.getUTCMonth() + 1) + ‘-‘ +
123                 f(this.getUTCDate()) + ‘T‘ +
124                 f(this.getUTCHours()) + ‘:‘ +
125                 f(this.getUTCMinutes()) + ‘:‘ +
126                 f(this.getUTCSeconds()) + ‘Z"‘;
127     };
128 
129 
130     Number.prototype.toJSONString = function () {
131 
132 // JSON numbers must be finite. Encode non-finite numbers as null.
133 
134         return isFinite(this) ? String(this) : ‘null‘;
135     };
136 
137 
138     Object.prototype.toJSONString = function () {
139         var a = [],     // The array holding the partial texts.
140             k,          // The current key.
141             v;          // The current value.
142 
143 // Iterate through all of the keys in the object, ignoring the proto chain
144 // and keys that are not strings.
145 
146         for (k in this) {
147             if (typeof k === ‘string‘ &&
148                     Object.prototype.hasOwnProperty.apply(this, [k])) {
149                 v = this[k];
150                 switch (typeof v) {
151                  case ‘object‘: if (v == this) continue; 
152 // Serialize a JavaScript object value. Ignore objects that lack the
153 // toJSONString method. Due to a specification error in ECMAScript,
154 // typeof null is ‘object‘, so watch out for that case.
155 
156                     if (v) {
157                         if (typeof v.toJSONString === ‘function‘) {
158                             a.push(k.toJSONString() + ‘:‘ + v.toJSONString());
159                         }
160                     } else {
161                         a.push(k.toJSONString() + ‘:null‘);
162                     }
163                     break;
164 
165                 case ‘string‘:
166                 case ‘number‘:
167                 case ‘boolean‘:
168                     a.push(k.toJSONString() + ‘:‘ + v.toJSONString());
169 
170 // Values without a JSON representation are ignored.
171 
172                 }
173             }
174         }
175 
176 // Join all of the member texts together and wrap them in braces.
177 
178         return ‘{‘ + a.join(‘,‘) + ‘}‘;
179     };
180 
181 
182     (function (s) {
183 
184 // Augment String.prototype. We do this in an immediate anonymous function to
185 // avoid defining global variables.
186 
187 // m is a table of character substitutions.
188 
189         var m = {
190             ‘\b‘: ‘\\b‘,
191             ‘\t‘: ‘\\t‘,
192             ‘\n‘: ‘\\n‘,
193             ‘\f‘: ‘\\f‘,
194             ‘\r‘: ‘\\r‘,
195             ‘"‘ : ‘\\"‘,
196             ‘\\‘: ‘\\\\‘
197         };
198 
199 
200         s.parseJSON = function (filter) {
201             var j;
202 
203             function walk(k, v) {
204                 var i;
205                 if (v && typeof v === ‘object‘) {
206                     for (i in v) {
207                         if (Object.prototype.hasOwnProperty.apply(v, [i])) {
208                             v[i] = walk(i, v[i]);
209                         }
210                     }
211                 }
212                 return filter(k, v);
213             }
214 
215 
216 // Parsing happens in three stages. In the first stage, we run the text against
217 // a regular expression which looks for non-JSON characters. We are especially
218 // concerned with ‘()‘ and ‘new‘ because they can cause invocation, and ‘=‘
219 // because it can cause mutation. But just to be safe, we will reject all
220 // unexpected characters.
221 
222 // We split the first stage into 3 regexp operations in order to work around
223 // crippling deficiencies in Safari‘s regexp engine. First we replace all
224 // backslash pairs with ‘@‘ (a non-JSON character). Second we delete all of
225 // the string literals. Third, we look to see if only JSON characters
226 // remain. If so, then the text is safe for eval.
227 
228             if (/^[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]*$/.test(this.
229                     replace(/\\./g, ‘@‘).
230                     replace(/"[^"\\\n\r]*"/g, ‘‘))) {
231 
232 // In the second stage we use the eval function to compile the text into a
233 // JavaScript structure. The ‘{‘ operator is subject to a syntactic ambiguity
234 // in JavaScript: it can begin a block or an object literal. We wrap the text
235 // in parens to eliminate the ambiguity.
236 
237                 j = eval(‘(‘ + this + ‘)‘);
238 
239 // In the optional third stage, we recursively walk the new structure, passing
240 // each name/value pair to a filter function for possible transformation.
241 
242                 return typeof filter === ‘function‘ ? walk(‘‘, j) : j;
243             }
244 
245 // If the text is not JSON parseable, then a SyntaxError is thrown.
246 
247             throw new SyntaxError(‘parseJSON‘);
248         };
249 
250 
251         s.toJSONString = function () {
252 
253 // If the string contains no control characters, no quote characters, and no
254 // backslash characters, then we can simply slap some quotes around it.
255 // Otherwise we must also replace the offending characters with safe
256 // sequences.
257 
258             if (/["\\\x00-\x1f]/.test(this)) {
259                 return ‘"‘ + this.replace(/[\x00-\x1f\\"]/g, function (a) {
260                     var c = m[a];
261                     if (c) {
262                         return c;
263                     }
264                     c = a.charCodeAt();
265                     return ‘\\u00‘ +
266                         Math.floor(c / 16).toString(16) +
267                         (c % 16).toString(16);
268                 }) + ‘"‘;
269             }
270             return ‘"‘ + this + ‘"‘;
271         };
272     })(String.prototype);
273 }