<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <script type="text/javascript"> var JSON; if (!JSON) { JSON = {}; } (function () { 'use strict'; function f(n) { // Format integers to have at least two digits. // 补齐 两位数 return n < 10 ? '0' + n : n; } // 在高级浏览器调用 (new Date() ).toJSON() "2017-07-28T01:27:34.790Z" , 所以下面是按照这个格式来模拟 if (typeof Date.prototype.toJSON !== 'function') { Date.prototype.toJSON = function (key) { return isFinite(this.valueOf()) ? this.getUTCFullYear() + '-' + f(this.getUTCMonth() + 1) + '-' + f(this.getUTCDate()) + 'T' + f(this.getUTCHours()) + ':' + f(this.getUTCMinutes()) + ':' + f(this.getUTCSeconds()) + 'Z' : null; }; //不支持toJSON 的浏览器可以取这些元素对象的 值 String.prototype.toJSON = Number.prototype.toJSON = Boolean.prototype.toJSON = function (key) { return this.valueOf(); }; } //过滤掉unicode特殊字符, 可以通过String.fromCharCode(parseInt(unicode),16)来输出,不过大部分unicode是『不可见』的,还是要通过unicode码表来查看 text.replace(/\\u[\dA-F]{4}/gi, function (match) { return String.fromCharCode(parseInt(match.replace(/\\u/g, ''), 16)); }); var cx = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g, //一些讨厌的特殊字符 escapable = /[\\\"\x00-\x1f\x7f-\x9f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g, gap, indent, meta = { // table of character substitutions 字符替换表格, 一些需要转义 '\b': '\\b', '\t': '\\t', '\n': '\\n', '\f': '\\f', '\r': '\\r', '"' : '\\"', '\\': '\\\\' }, rep; function quote(string) { // If the string contains no control characters, no quote characters, and no // backslash characters, then we can safely slap some quotes around it. // Otherwise we must also replace the offending characters with safe escape // sequences. // 如果字符串包涵了 控制字符? 引号, 反斜杠, 我们就必须把这些讨厌的字符给替换成安全的, 否则我们把这些用引号给包裹起来, escapable.lastIndex = 0; return escapable.test(string) ? '"' + string.replace(escapable, function (a) { var c = meta[a]; return typeof c === 'string' ? c : '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4); }) + '"' : '"' + string + '"'; } function str(key, holder) { // Produce a string from holder[key]. var i, // The loop counter. k, // The member key. v, // The member value. length, mind = gap, partial, value = holder[key]; // If the value has a toJSON method, call it to obtain a replacement value. // 如果有toJSON方法, 调用生成序列化字符串 if (value && typeof value === 'object' && typeof value.toJSON === 'function') { value = value.toJSON(key); } // If we were called with a replacer function, then call the replacer to // obtain a replacement value. 如有有替代的函数 if (typeof rep === 'function') { value = rep.call(holder, key, value); } // What happens next depends on the value's type. vule的类型决定下一步干什么 switch (typeof value) { case 'string': return quote(value); case 'number': // JSON numbers must be finite. Encode non-finite numbers as null. 如果无限的值被转成 null return isFinite(value) ? String(value) : 'null'; case 'boolean': case 'null': // If the value is a boolean or null, convert it to a string. Note: // typeof null does not produce 'null'. The case is included here in // the remote chance that this gets fixed someday. // 如果值是 boolean null, 转成 'true' 'false' 'null'; 虽然typeof null 不会是‘null’ , 但以后有机会被修正成'null', 所以这里我们也把这种情况包含进来 return String(value); // If the type is 'object', we might be dealing with an object or an array or // null. case 'object': // Due to a specification blunder in ECMAScript, typeof null is 'object', // so watch out for that case. if (!value) { return 'null'; } // Make an array to hold the partial results of stringifying this object value. // 用一个数组保存部分已被序列化的结果 gap += indent; partial = []; // Is the value an array? if (Object.prototype.toString.apply(value) === '[object Array]') { // The value is an array. Stringify every element. Use null as a placeholder // for non-JSON values. length = value.length; for (i = 0; i < length; i += 1) { //如果数组, 递归调用str partial[i] = str(i, value) || 'null'; } // Join all of the elements together, separated with commas, and wrap them in // brackets. 组合所有的元素以前, 用逗号分隔, 用括号包裹 v = partial.length === 0 ? '[]' : gap ? '[\n' + gap + partial.join(',\n' + gap) + '\n' + mind + ']' : '[' + partial.join(',') + ']'; gap = mind; return v; } // If the replacer is an array, use it to select the members to be stringified. if (rep && typeof rep === 'object') { length = rep.length; for (i = 0; i < length; i += 1) { if (typeof rep[i] === 'string') { k = rep[i]; v = str(k, value); if (v) { partial.push(quote(k) + (gap ? ': ' : ':') + v); } } } } else { // Otherwise, iterate through all of the keys in the object. for (k in value) { if (Object.prototype.hasOwnProperty.call(value, k)) { v = str(k, value); if (v) { partial.push(quote(k) + (gap ? ': ' : ':') + v); } } } } // Join all of the member texts together, separated with commas, // and wrap them in braces. v = partial.length === 0 ? '{}' : gap ? '{\n' + gap + partial.join(',\n' + gap) + '\n' + mind + '}' : '{' + partial.join(',') + '}'; gap = mind; return v; } } // If the JSON object does not yet have a stringify method, give it one. if (typeof JSON.stringify !== 'function'||(navigator.userAgent.indexOf("MSIE 8.0")>0)) { JSON.stringify = function (value, replacer, space) { // The stringify method takes a value and an optional replacer, and an optional // space parameter, and returns a JSON text. The replacer can be a function // that can replace values, or an array of strings that will select the keys. // A default replacer method can be provided. Use of the space parameter can // produce text that is more easily readable. var i; gap = ''; indent = ''; // If the space parameter is a number, make an indent string containing that // many spaces. if (typeof space === 'number') { for (i = 0; i < space; i += 1) { indent += ' '; } // If the space parameter is a string, it will be used as the indent string. } else if (typeof space === 'string') { indent = space; } // If there is a replacer, it must be a function or an array. // Otherwise, throw an error. rep = replacer; if (replacer && typeof replacer !== 'function' && (typeof replacer !== 'object' || typeof replacer.length !== 'number')) { throw new Error('JSON.stringify'); } // Make a fake root object containing our value under the key of ''. // Return the result of stringifying the value. return str('', {'': value}); }; } // If the JSON object does not yet have a parse method, give it one. if (typeof JSON.parse !== 'function') { JSON.parse = function (text, reviver) { // The parse method takes a text and an optional reviver function, and returns // a JavaScript value if the text is a valid JSON text. var j; function walk(holder, key) { // The walk method is used to recursively walk the resulting structure so // that modifications can be made. var k, v, value = holder[key]; if (value && typeof value === 'object') { for (k in value) { if (Object.prototype.hasOwnProperty.call(value, k)) { v = walk(value, k); if (v !== undefined) { value[k] = v; } else { delete value[k]; } } } } return reviver.call(holder, key, value); } // Parsing happens in four stages. In the first stage, we replace certain // Unicode characters with escape sequences. JavaScript handles many characters // incorrectly, either silently deleting them, or treating them as line endings. text = String(text); cx.lastIndex = 0; if (cx.test(text)) { text = text.replace(cx, function (a) { return '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4); }); } // In the second stage, we run the text against regular expressions that look // for non-JSON patterns. We are especially concerned with '()' and 'new' // because they can cause invocation, and '=' because it can cause mutation. // But just to be safe, we want to reject all unexpected forms. // We split the second stage into 4 regexp operations in order to work around // crippling inefficiencies in IE's and Safari's regexp engines. First we // replace the JSON backslash pairs with '@' (a non-JSON character). Second, we // replace all simple value tokens with ']' characters. Third, we delete all // open brackets that follow a colon or comma or that begin the text. Finally, // we look to see that the remaining characters are only whitespace or ']' or // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval. //先把无意义的 字符替换成空, 在看看结果是不是符合JSON格式 if (/^[\],:{}\s]*$/ .test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@') .replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']') .replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) { // In the third stage we use the eval function to compile the text into a // JavaScript structure. The '{' operator is subject to a syntactic ambiguity // in JavaScript: it can begin a block or an object literal. We wrap the text // in parens to eliminate the ambiguity. j = eval('(' + text + ')'); // In the optional fourth stage, we recursively walk the new structure, passing // each name/value pair to a reviver function for possible transformation. return typeof reviver === 'function' ? walk({'': j}, '') : j; } // If the text is not JSON parseable, then a SyntaxError is thrown. throw new SyntaxError('JSON.parse'); }; } }()); </script> </body> </html>