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parse()用法

 1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 2 <html xmlns="http://www.w3.org/1999/xhtml">
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
 5     <title>JSON</title>
 6     <script type="text/javascript" src="createXHR.js"></script>
 7     <script type="text/javascript" src="json_parse.js"></script>
 8     <script type="text/javascript" src="test01.js"></script>
 9 </head>
10 <body>
11     <div id="contacts"></div>
12 </body>
13 </html>

createXHR.js

 1 function createXHR() {
 2     if (typeof XMLHttpRequest != "undefined") {
 3         return new XMLHttpRequest();
 4     } else if (typeof ActiveXObject != "undefined") {
 5         if (typeof arguments.callee.activeXString != "string") {
 6             var versions = ["MSXML2.XMLHttp.6.0", "MSXML2.XMLHttp.3.0", "MSXML2.XMLHttp"];
 7             for (var i = 0, len = versions.length; i < len; i++) {
 8                 try {
 9                     var xhr = new ActiveXObject(versions[i]);
10                     arguments.callee.activeXString = versions[i];
11                     return xhr;
12                 } catch (ex) {
13                     console.log("异常");
14                 }
15             }
16         }
17         return new ActiveXObject(arguments.callee.activeXString);
18     } else {
19         throw new Error("No XHR object available.");
20     }
21 }

json_parse.js

  1 /*
  2     json_parse.js
  3     2011-03-06
  4 
  5     Public Domain.
  6 
  7     NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
  8 
  9     This file creates a json_parse function.
 10 
 11         json_parse(text, reviver)
 12             This method parses a JSON text to produce an object or array.
 13             It can throw a SyntaxError exception.
 14 
 15             The optional reviver parameter is a function that can filter and
 16             transform the results. It receives each of the keys and values,
 17             and its return value is used instead of the original value.
 18             If it returns what it received, then the structure is not modified.
 19             If it returns undefined then the member is deleted.
 20 
 21             Example:
 22 
 23             // Parse the text. Values that look like ISO date strings will
 24             // be converted to Date objects.
 25 
 26             myData = json_parse(text, function (key, value) {
 27                 var a;
 28                 if (typeof value === 'string') {
 29                     a =
 30 /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
 31                     if (a) {
 32                         return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
 33                             +a[5], +a[6]));
 34                     }
 35                 }
 36                 return value;
 37             });
 38 
 39     This is a reference implementation. You are free to copy, modify, or
 40     redistribute.
 41 
 42     This code should be minified before deployment.
 43     See http://javascript.crockford.com/jsmin.html
 44 
 45     USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
 46     NOT CONTROL.
 47 */
 48 
 49 /*members "", "\"", "\/", "\\", at, b, call, charAt, f, fromCharCode,
 50     hasOwnProperty, message, n, name, prototype, push, r, t, text
 51 */
 52 
 53 var json_parse = (function () {
 54     "use strict";
 55 
 56 // This is a function that can parse a JSON text, producing a JavaScript
 57 // data structure. It is a simple, recursive descent parser. It does not use
 58 // eval or regular expressions, so it can be used as a model for implementing
 59 // a JSON parser in other languages.
 60 
 61 // We are defining the function inside of another function to avoid creating
 62 // global variables.
 63 
 64     var at,     // The index of the current character
 65         ch,     // The current character
 66         escapee = {
 67             '"':  '"',
 68             '\\': '\\',
 69             '/':  '/',
 70             b:    '\b',
 71             f:    '\f',
 72             n:    '\n',
 73             r:    '\r',
 74             t:    '\t'
 75         },
 76         text,
 77 
 78         error = function (m) {
 79 
 80 // Call error when something is wrong.
 81 
 82             throw {
 83                 name:    'SyntaxError',
 84                 message: m,
 85                 at:      at,
 86                 text:    text
 87             };
 88         },
 89 
 90         next = function (c) {
 91 
 92 // If a c parameter is provided, verify that it matches the current character.
 93 
 94             if (c && c !== ch) {
 95                 error("Expected '" + c + "' instead of '" + ch + "'");
 96             }
 97 
 98 // Get the next character. When there are no more characters,
 99 // return the empty string.
100 
101             ch = text.charAt(at);
102             at += 1;
103             return ch;
104         },
105 
106         number = function () {
107 
108 // Parse a number value.
109 
110             var number,
111                 string = '';
112 
113             if (ch === '-') {
114                 string = '-';
115                 next('-');
116             }
117             while (ch >= '0' && ch <= '9') {
118                 string += ch;
119                 next();
120             }
121             if (ch === '.') {
122                 string += '.';
123                 while (next() && ch >= '0' && ch <= '9') {
124                     string += ch;
125                 }
126             }
127             if (ch === 'e' || ch === 'E') {
128                 string += ch;
129                 next();
130                 if (ch === '-' || ch === '+') {
131                     string += ch;
132                     next();
133                 }
134                 while (ch >= '0' && ch <= '9') {
135                     string += ch;
136                     next();
137                 }
138             }
139             number = +string;
140             if (!isFinite(number)) {
141                 error("Bad number");
142             } else {
143                 return number;
144             }
145         },
146 
147         string = function () {
148 
149 // Parse a string value.
150 
151             var hex,
152                 i,
153                 string = '',
154                 uffff;
155 
156 // When parsing for string values, we must look for " and \ characters.
157 
158             if (ch === '"') {
159                 while (next()) {
160                     if (ch === '"') {
161                         next();
162                         return string;
163                     } else if (ch === '\\') {
164                         next();
165                         if (ch === 'u') {
166                             uffff = 0;
167                             for (i = 0; i < 4; i += 1) {
168                                 hex = parseInt(next(), 16);
169                                 if (!isFinite(hex)) {
170                                     break;
171                                 }
172                                 uffff = uffff * 16 + hex;
173                             }
174                             string += String.fromCharCode(uffff);
175                         } else if (typeof escapee[ch] === 'string') {
176                             string += escapee[ch];
177                         } else {
178                             break;
179                         }
180                     } else {
181                         string += ch;
182                     }
183                 }
184             }
185             error("Bad string");
186         },
187 
188         white = function () {
189 
190 // Skip whitespace.
191 
192             while (ch && ch <= ' ') {
193                 next();
194             }
195         },
196 
197         word = function () {
198 
199 // true, false, or null.
200 
201             switch (ch) {
202             case 't':
203                 next('t');
204                 next('r');
205                 next('u');
206                 next('e');
207                 return true;
208             case 'f':
209                 next('f');
210                 next('a');
211                 next('l');
212                 next('s');
213                 next('e');
214                 return false;
215             case 'n':
216                 next('n');
217                 next('u');
218                 next('l');
219                 next('l');
220                 return null;
221             }
222             error("Unexpected '" + ch + "'");
223         },
224 
225         value,  // Place holder for the value function.
226 
227         array = function () {
228 
229 // Parse an array value.
230 
231             var array = [];
232 
233             if (ch === '[') {
234                 next('[');
235                 white();
236                 if (ch === ']') {
237                     next(']');
238                     return array;   // empty array
239                 }
240                 while (ch) {
241                     array.push(value());
242                     white();
243                     if (ch === ']') {
244                         next(']');
245                         return array;
246                     }
247                     next(',');
248                     white();
249                 }
250             }
251             error("Bad array");
252         },
253 
254         object = function () {
255 
256 // Parse an object value.
257 
258             var key,
259                 object = {};
260 
261             if (ch === '{') {
262                 next('{');
263                 white();
264                 if (ch === '}') {
265                     next('}');
266                     return object;   // empty object
267                 }
268                 while (ch) {
269                     key = string();
270                     white();
271                     next(':');
272                     if (Object.hasOwnProperty.call(object, key)) {
273                         error('Duplicate key "' + key + '"');
274                     }
275                     object[key] = value();
276                     white();
277                     if (ch === '}') {
278                         next('}');
279                         return object;
280                     }
281                     next(',');
282                     white();
283                 }
284             }
285             error("Bad object");
286         };
287 
288     value = function () {
289 
290 // Parse a JSON value. It could be an object, an array, a string, a number,
291 // or a word.
292 
293         white();
294         switch (ch) {
295         case '{':
296             return object();
297         case '[':
298             return array();
299         case '"':
300             return string();
301         case '-':
302             return number();
303         default:
304             return ch >= '0' && ch <= '9' ? number() : word();
305         }
306     };
307 
308 // Return the json_parse function. It will have access to all of the above
309 // functions and variables.
310 
311     return function (source, reviver) {
312         var result;
313 
314         text = source;
315         at = 0;
316         ch = ' ';
317         result = value();
318         white();
319         if (ch) {
320             error("Syntax error");
321         }
322 
323 // If there is a reviver function, we recursively walk the new structure,
324 // passing each name/value pair to the reviver function for possible
325 // transformation, starting with a temporary root object that holds the result
326 // in an empty key. If there is not a reviver function, we simply return the
327 // result.
328 
329         return typeof reviver === 'function' ? (function walk(holder, key) {
330             var k, v, value = holder[key];
331             if (value && typeof value === 'object') {
332                 for (k in value) {
333                     if (Object.prototype.hasOwnProperty.call(value, k)) {
334                         v = walk(value, k);
335                         if (v !== undefined) {
336                             value[k] = v;
337                         } else {
338                             delete value[k];
339                         }
340                     }
341                 }
342             }
343             return reviver.call(holder, key, value);
344         }({'': result}, '')) : result;
345     };
346 }());

test01.js

 1 var xhr = createXHR();
 2 xhr.onreadystatechange = function() {
 3     if (xhr.readyState == 4) {
 4         if ((xhr.status >= 200 && xhr.status < 300) || xhr.status == 304) {
 5             var contacts = JSON.parse(xhr.responseText);
 6             var list = document.getElementById("contacts");
 7             for (var i = 0, len = contacts.length; i < len; i++) {
 8                 var li = document.createElement("li");
 9                 li.innerHTML = "<a href=\"mailto:" + contacts[i].email + "\">" + contacts[i].name + "</a>";
10                 list.appendChild(li);
11             }
12         }
13     }
14 };
15 
16 xhr.open("get", "test01.json", true);
17 xhr.send(null);

test01.json

 1 [{
 2     "name": "Nicholas C. Zakas",
 3     "email": "nicholas@some-domain-name.com"
 4 }, {
 5     "name": "Jim Smith",
 6     "email": "jimsith@some-domain-name.com"
 7 }, {
 8     "name": "Michael Jones",
 9     "email": "mj@some-domain-name.com"
10 }]

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原文地址：https://www.cnblogs.com/qzsonline/p/2540323.html