js里json和eval()
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JSON
* - JS中的对象只有JS自己认识，其他的语言都不认识
* - JSON就是一个特殊格式的字符串，这个字符串可以被任意的语言所识别，
* 并且可以转换为任意语言中的对象，JSON在开发中主要用来数据的交互
* - JSON
* - javascript Object Notation JS对象表示法
* - JSON和JS对象的格式一样，只不过JSON字符串中的属性名必须加双引号
* 其他的和JS语法一致
* JSON分类：
* 1.对象 {}
* 2.数组 []
*
* JSON中允许的值：
* 1.字符串
* 2.数值
* 3.布尔值
* 4.null
* 5.对象
* 6.数组
var arr = ‘[1,2,3,"hello",true]‘; var obj2 = ‘{"arr":[1,2,3]}‘; var arr2 =‘[{"name":"孙悟空","age":18,"gender":"男"},{"name":"孙悟空","age":18,"gender":"男"}]‘;
var json = ‘{"name":"孙悟空","age":18,"gender":"男"}‘;
* JS对象 ---> JSON
* JSON.stringify()
* - 可以将一个JS对象转换为JSON字符串
* - 需要一个js对象作为参数，会返回一个JSON字符串
var o = JSON.parse(json); var o2 = JSON.parse(arr);
var json = ‘{"name":"孙悟空","age":18,"gender":"男"}‘; var str = JSON.stringify(obj3);
var str3 = ‘{"name":"孙悟空","age":18,"gender":"男"}‘; JSON.parse(str3);
JSON这个对象在IE7及以下的浏览器中不支持，所以在这些浏览器中调用时会报错
eval()
* - 这个函数可以用来执行一段字符串形式的JS代码，并将执行结果返回
* - 如果使用eval()执行的字符串中含有{},它会将{}当成是代码块
* 如果不希望将其当成代码块解析，则需要在字符串前后各加一个()
*
* - eval()这个函数的功能很强大，可以直接执行一个字符串中的js代码，
* 但是在开发中尽量不要使用，首先它的执行性能比较差，然后它还具有安全隐患
*/
var str2 = "alert(‘hello‘);"; var obj = eval("("+str+")");
可以引入json.js达到兼容
// json2.js // 2016-05-01 // Public Domain. // NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK. // See http://www.JSON.org/js.html // This code should be minified before deployment. // See http://javascript.crockford.com/jsmin.html // USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO // NOT CONTROL. // This file creates a global JSON object containing two methods: stringify // and parse. This file is provides the ES5 JSON capability to ES3 systems. // If a project might run on IE8 or earlier, then this file should be included. // This file does nothing on ES5 systems. // JSON.stringify(value, replacer, space) // value any JavaScript value, usually an object or array. // replacer an optional parameter that determines how object // values are stringified for objects. It can be a // function or an array of strings. // space an optional parameter that specifies the indentation // of nested structures. If it is omitted, the text will // be packed without extra whitespace. If it is a number, // it will specify the number of spaces to indent at each // level. If it is a string (such as " " or " "), // it contains the characters used to indent at each level. // This method produces a JSON text from a JavaScript value. // When an object value is found, if the object contains a toJSON // method, its toJSON method will be called and the result will be // stringified. A toJSON method does not serialize: it returns the // value represented by the name/value pair that should be serialized, // or undefined if nothing should be serialized. The toJSON method // will be passed the key associated with the value, and this will be // bound to the value. // For example, this would serialize Dates as ISO strings. // Date.prototype.toJSON = function (key) { // function f(n) { // // Format integers to have at least two digits. // return (n < 10) // ? "0" + n // : n; // } // return this.getUTCFullYear() + "-" + // f(this.getUTCMonth() + 1) + "-" + // f(this.getUTCDate()) + "T" + // f(this.getUTCHours()) + ":" + // f(this.getUTCMinutes()) + ":" + // f(this.getUTCSeconds()) + "Z"; // }; // You can provide an optional replacer method. It will be passed the // key and value of each member, with this bound to the containing // object. The value that is returned from your method will be // serialized. If your method returns undefined, then the member will // be excluded from the serialization. // If the replacer parameter is an array of strings, then it will be // used to select the members to be serialized. It filters the results // such that only members with keys listed in the replacer array are // stringified. // Values that do not have JSON representations, such as undefined or // functions, will not be serialized. Such values in objects will be // dropped; in arrays they will be replaced with null. You can use // a replacer function to replace those with JSON values. // JSON.stringify(undefined) returns undefined. // The optional space parameter produces a stringification of the // value that is filled with line breaks and indentation to make it // easier to read. // If the space parameter is a non-empty string, then that string will // be used for indentation. If the space parameter is a number, then // the indentation will be that many spaces. // Example: // text = JSON.stringify(["e", {pluribus: "unum"}]); // // text is ‘["e",{"pluribus":"unum"}]‘ // text = JSON.stringify(["e", {pluribus: "unum"}], null, " "); // // text is ‘[ "e", { "pluribus": "unum" } ]‘ // text = JSON.stringify([new Date()], function (key, value) { // return this[key] instanceof Date // ? "Date(" + this[key] + ")" // : value; // }); // // text is ‘["Date(---current time---)"]‘ // JSON.parse(text, reviver) // This method parses a JSON text to produce an object or array. // It can throw a SyntaxError exception. // The optional reviver parameter is a function that can filter and // transform the results. It receives each of the keys and values, // and its return value is used instead of the original value. // If it returns what it received, then the structure is not modified. // If it returns undefined then the member is deleted. // Example: // // Parse the text. Values that look like ISO date strings will // // be converted to Date objects. // myData = JSON.parse(text, function (key, value) { // var a; // if (typeof value === "string") { // a = // /^(d{4})-(d{2})-(d{2})T(d{2}):(d{2}):(d{2}(?:.d*)?)Z$/.exec(value); // if (a) { // return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4], // +a[5], +a[6])); // } // } // return value; // }); // myData = JSON.parse(‘["Date(09/09/2001)"]‘, function (key, value) { // var d; // if (typeof value === "string" && // value.slice(0, 5) === "Date(" && // value.slice(-1) === ")") { // d = new Date(value.slice(5, -1)); // if (d) { // return d; // } // } // return value; // }); // This is a reference implementation. You are free to copy, modify, or // redistribute. /*jslint eval, for, this */ /*property JSON, apply, call, charCodeAt, getUTCDate, getUTCFullYear, getUTCHours, getUTCMinutes, getUTCMonth, getUTCSeconds, hasOwnProperty, join, lastIndex, length, parse, prototype, push, replace, slice, stringify, test, toJSON, toString, valueOf */ // Create a JSON object only if one does not already exist. We create the // methods in a closure to avoid creating global variables. if (typeof JSON !== "object") { JSON = {}; } (function () { "use strict"; var rx_one = /^[],:{}s]*$/; var rx_two = /\(?:["\/bfnrt]|u[0-9a-fA-F]{4})/g; var rx_three = /"[^"\ ]*"|true|false|null|-?d+(?:.d*)?(?:[eE][+-]?d+)?/g; var rx_four = /(?:^|:|,)(?:s*[)+/g; var rx_escapable = /[\"u0000-u001fu007f-u009fu00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g; var rx_dangerous = /[u0000u00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g; function f(n) { // Format integers to have at least two digits. return n < 10 ? "0" + n : n; } function this_value() { return this.valueOf(); } if (typeof Date.prototype.toJSON !== "function") { Date.prototype.toJSON = function () { 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; }; Boolean.prototype.toJSON = this_value; Number.prototype.toJSON = this_value; String.prototype.toJSON = this_value; } var gap; var indent; var meta; var 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. rx_escapable.lastIndex = 0; return rx_escapable.test(string) ? """ + string.replace(rx_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. var k; // The member key. var v; // The member value. var length; var mind = gap; var partial; var value = holder[key]; // If the value has a toJSON method, call it to obtain a replacement value. 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. if (typeof rep === "function") { value = rep.call(holder, key, value); } // What happens next depends on the value‘s type. switch (typeof value) { case "string": return quote(value); case "number": // JSON numbers must be finite. Encode non-finite numbers as 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. 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. 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) { partial[i] = str(i, value) || "null"; } // Join all of the elements together, separated with commas, and wrap them in // brackets. v = partial.length === 0 ? "[]" : gap ? "[ " + gap + partial.join(", " + gap) + " " + 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 ? "{ " + gap + partial.join(", " + gap) + " " + 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") { meta = { // table of character substitutions "": "\b", " ": "\t", " ": "\n", "f": "\f", " ": "\r", """: "\"", "\": "\\" }; 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; var v; var 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); rx_dangerous.lastIndex = 0; if (rx_dangerous.test(text)) { text = text.replace(rx_dangerous, 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. if ( rx_one.test( text .replace(rx_two, "@") .replace(rx_three, "]") .replace(rx_four, "") ) ) { // 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"); }; } }());