JavaScript对象遍历

一、对象是数组:

var arr = [9, 8, 7, 6, 5, 4, 3, 2, 1]; //each遍历：$.each(arr,function (index,value) {    alert(index)})                   //0 1 2 3 4 5 6 7 8$.each(arr,function (index,value) {    alert(value)})                  //9 8 7 6 5  4 3 2 1     $.each(arr,function () {    alert(this)})                                     //9 8 7 6 5  4 3 2 1     ---------------------------------------------------------//for遍历：for (var i in arr) {                //不推荐for in 遍历数组    console.log(arr[i]);}                                   //9 8 7 6 5  4 3 2 1     for (var i = 0; i < arr.length; i++) {    console.log(arr[i]);}                                   //9 8 7 6 5  4 3 2 1      

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var arr = [{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}]; $.each(arr, function(index, obj) {    alert(index);          // 0,1,2,3,4     alert(obj);            //{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"}...    alert(obj.id);         // 1,2,3,4,5    alert(obj.tagName);    // apple, orange, banana, watermelon, pineapple});                       $.each(arr, function(index, obj) {    alert("第"+ index +"项的tagName是"+obj.tagName);});                         //第0项的tagName是apple  第1项的tagName是orange..................

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二、对象是json:

var json  =  { "jim": "11", "tom": "12", "lilei": "13" }; //jquery获取$.each(json , function(key, value) {     alert(key);                  //jim  tom  lilei          alert(value);                //11  12  13     }); //原生JS获取for(var i in json){    alert(i);                   //jim  tom  lilei    alert(json[i]);             //11  12  13};

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三、json是字符串:（解决方案：JSON字符串转换为JavaScript对象。）

var json = '[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}]';//用$.parseJSON(json)或者JSON.parse(json)将其转换为JavaScript对象   字符串转json对象$.each($.parseJSON(json), function(idx, obj) {            alert(obj.tagName);          //apple, orange, banana, watermelon, pineapple});    

json的解析方法共有两种：eval() 和 JSON.parse()，使用方法如下：

var jsonData = '{"data1":"Hello", "data2":"world"}';eval("("+jsonData+")");             //Object {data1: "Hello", data2: "world"}                      JSON.parse(jsonData);               //Object {data1: "Hello", data2: "world"}

这样就把jsonData这个json格式的字符串转换成了JSON对象。

eval("("+data+")");                 //转换为json对象

eval在解析字符串时，会执行该字符串中的代码（这样的后果是相当恶劣的）

var obj= [{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}];JSON.stringify(obj)                //json对象转字符串  与JSON.parse()相反"[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}]"