JSON作為一種輕量的數據傳輸格式，越來越受到人們的青睞。下面是我仿照Prototype的一些實現。

JSONFilter:/^///*-secure-([/s/S]*)/*///s*$/,

unfilterJSON:function(json,filter) {

????return json.replace((filter || dom.JSONFilter), function(a,b){

????????return b || ""

????});

},

JSONFilter完全抄自Prototype，因為后臺基本上只會傳輸兩種格式的東西給我們——文本（xmlhttp.responseText）與XML（xmlhttp.responseXML）。如果要json，我們可以eval一下，或者使用現代瀏覽器提供的JSON.parse方法。但問題就出在eval中，很容易出現XSS攻擊。如果文本是注釋就可以避免這問題，在Prototype中還檢察一下請求的來源。對于自家的網站的請求，我們完全可以在請求前處理一下，讓它變成如下格式：

var text = '/*-secure-/n{"name": "Violet", "occupation": "character", "age": 25}/n*/'

?dom.unfilterJSON(text)

// -> '{"name": "Violet", "occupation": "character", "age": 25}'

到時我們用unfilterJSON函數提取合法的字段來eval就沒問題了。

第二個函數，判斷字符串是否符合JSON的格式。JSON是有固定的格式，要求鍵必須被雙引號括起來。下面的函數提取自json2：

isJSONText:function(json){//

????return /^[/],:{}/s]*$/.test(json.replace(///(?:["bfnrt]|u[0-9a-fA-F]{4})/g, "@")

????????.replace(/"[^"///n/r]*"|true|false|null|-?/d+(?:/./d*)?(?:[eE][+/-]?/d+)?/g, "]")

????????.replace(/(?:^|:|,)(?:/s*/[)+/g, ""));

},

第三個函數，將符合JSON的格式的文本變成JSON對象。第二參數用于指明此文本是否安全（如，是否同源請求）。如果能用原生對象的parse方法就用原生的，否則動態解析它。之所以不用eval，是因為ecma那幫人頭腦發熱，想禁掉它。

????????evalJSON: function( json ,sanitize) {??

????????????if ( !is(json,"String") || !json )

????????????????return null;

????????????json = dom.unfilterJSON(json);

????????????//判定是否符合JSON的格式 from http://json.org/json2.js

????????????if ( !sanitize || dom.isJSONText(json) ) {

????????????????return window.JSON && window.JSON.parse ?

????????????????window.JSON.parse( json ) : (new Function("return " + json))();

????????????} else {

????????????????throw? "Invalid JSON: " + json;

????????????}

????????}

//http://www.21kaiyun.com

var data =dom.evalJSON( '{ "name": "Violet", "occupation": "character" }');

data.name;

//-> "Violet"

第四函數，將JSON對象變成文本。

// http://www.21kaiyun.com //21世紀開運網?

//?? var a = [1,2,3,4,{aa:8}]; puts(dom.toJSON(a))

toJSON:function(obj){

????if (window.JSON && window.JSON.stringify) {

????????return JSON.stringify(obj)

????}

????if (typeof window.uneval == 'function') {

????????return uneval(obj);

????}

????if (typeof obj == 'object') {

????????if (!obj) {

????????????return 'null';

????????}

????????var list = [];

????????if (dom.is(obj,"Array")) {

????????????for (var i=0,n=obj.length;i <n;i++) {

????????????????list.push(dom.toJSON(obj[i]));

????????????}

????????????return '[' + list.join(',') + ']';

????????} else {

????????????for (var prop in obj) {

????????????????if(obj[has](prop))

????????????????????list.push('"' + prop + '":' + dom.toJSON(obj[prop]));

????????????}

????????????return '{' + list.join(',') + '}';

????????}

????} else if (typeof obj == 'string') {

????????return '"' + obj.replace(/(["'])/g, '//$1') + '"';

????} else {

????????return new String(obj);

????}

},

toJSON : function(obj) {

????if(is(window.JSON,"JSON")){

????????return JSON.stringify(obj)

????}

????function f(n) {

????????return n < 10 ? '0' + n : n;

????}

????var escapable = /[///"/x00-/x1f/x7f-/x9f/u00ad/u0600-/u0604/u070f/u17b4/u17b5/u200c-/u200f/u2028-/u202f/u2060-/u206f/ufeff/ufff0-/uffff]/g;

????var meta = {

????????'/b': '//b',

????????'/t': '//t',

????????'/n': '//n',

????????'/f': '//f',

????????'/r': '//r',

????????'"' : '//"',

????????'//': ''

????};

????function _char(c) {

????????return meta[c] ? meta[c] :'//u'+('0000'+(+(c.charCodeAt(0))).toString(16)).slice(-4);

????}

????function _string(s) {

????????return '"' + s.replace(escapable, _char) + '"';

????}

????if(is(obj,"Date")){

????????return? '"' + obj.getUTCFullYear() + '-' +

????????f(obj.getUTCMonth() + 1) + '-' +

????????f(obj.getUTCDate())????? + 'T' +

????????f(obj.getUTCHours())???? + ':' +

????????f(obj.getUTCMinutes())?? + ':' +

????????f(obj.getUTCSeconds())?? + 'Z"' ;

????}else if(is(obj,"Number")){

????????return isFinite(obj) ? obj+'' : 'null';

????}else if(is(obj,"Boolean")){

????????return? obj+''

????}else if(is(obj,"String")){

????????return _string(obj)

????}else if(obj === null){

????????return "null"

????}else if(is(obj,"Array")){

????????return '[' + (dom.filter(obj,function(value){

????????????return dom.toJSON(value) !== undefined;

????????})).join(', ') + ']';

????}else if(is(obj,"Object")){

????????var results = [];

????????dom.each(obj,function(value,key){

????????????value = dom.toJSON(value)

????????????if (!value)

????????????????results.push(dom.toJSON(key) + ': ' + value);

????????});

????????return '{' + results.join(', ') + '}';

????}else {

????????return undefined;

????}

},

?

Is函數

?

目前最精確的判定方法（不包括自定義類型）

//2010.6.1更新

????????var is = function (obj,type) {

????????return (type === "Null" && obj === null) ||

????????(type === "Undefined" && obj === void 0 ) ||

????????(type === "Number" && isFinite(obj)) ||

?????????Object.prototype.toString.call(obj).slice(8,-1) === type;

????},

用法如下：

//***************示例一，判定數組與函數

????????var forEach = function(array,fn,bind){

??????????if(is(array,"Array") && is(Array.forEach,"Function")){

????????????array.forEach(fn,bind);

??????????}else{

????????????for(var i=0,n=array.length;i<n;i++){

??????????????i in array && fn.call(bind,array[i],i,array)

????????????}

??????????}

????????}

//***************示例二，判定null

var a = null

alert(is(a,"Null"))

//***************示例二，判定undefined

var b

alert(is(b,"Undefined"))

另一個變種，直接返回表示類型的字符串

var getType = function (obj) {

??var _toString = Object.prototype.toString,undefined;

??return obj === null? "Null":

????obj === undefined ? "Undefined":

????_toString.call(obj).slice(8,-1);

};

用法：

var arr = [1,2,3,4]

??????alert(getType(arr));//Array

??????var nil = null

??????alert(getType(nil))//Null

??????var und ;

??????alert(getType(und))//Undefined

??????var spans = document.getElementsByTagName("span");

??????alert(getType(spans)) //HTMLCollection

??????alert(getType(spans[0].childNodes))//NodeList

//2010.7.20

function isA (thing, canon) {

??// special case for null and undefined

??if (thing == null || canon == null) {

????return thing === canon;

??}

??return Object.getPrototypeOf(Object(thing)) == Object.getPrototypeOf(Object(canon));

}

function isBool (thing) {

??return isA(thing, true);

}

function isNumber (thing) {

??return isA(thing, 0) && isFinite(thing);

}

function isString (thing) {

??return isA(thing, "");

}

總結

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