JQuery $.each遍历JavaScript数组对象实例教程

查看一个简单的jquery的例子来遍历一个javascript数组对象。

var json = [
{"id":"1","tagname":"apple"},
{"id":"2","tagname":"orange"},
{"id":"3","tagname":"banana"},
{"id":"4","tagname":"watermelon"},
{"id":"5","tagname":"pineapple"}
];

$.each(json, function(idx, obj) {
alert(obj.tagname);
});

上面的代码片断工作正常，提示 “apple”, “orange” … 等，如预期一样。
问题: json 字符串

下面的例子中，声明了一个json字符串（随附单或双引号）直接地。

var json = '[{"id":"1","tagname":"apple"},{"id":"2","tagname":"orange"},
{"id":"3","tagname":"banana"},{"id":"4","tagname":"watermelon"},
{"id":"5","tagname":"pineapple"}]';

$.each(json, function(idx, obj) {
alert(obj.tagname);
});

在chrome中，它显示在控制台下面的错误：

uncaught typeerror: cannot use 'in' operator to search for '156'
in [{"id":"1","tagname":"apple"}...

解决方案：json字符串转换为javascript对象。
要修复它，通过标准json.parse()或jquery 的 $.parsejson 将其转换为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"}]';

$.each(json.parse(json), function(idx, obj) {
alert(obj.tagname);
});

//or 

$.each($.parsejson(json), function(idx, obj) {
alert(obj.tagname);
});