jQuery: 遍历json字符串, 遍历object数组，报错：Uncaught TypeError: Cannot use ‘in’ operator to search for ‘156’, Uncaught SyntaxError: Unexpected token k in JSON at position 2, loop over JSON string – $.each example

遍历一个json字符串，或者object数组的方法：

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);
});

Above code snippet is working fine, prompts the “apple”, “orange” … as expected.

问题来了 Problem: JSON string

现在定义一个json字符串的话，我们再试试：

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console调试面板上，直接报错：

Uncaught TypeError: Cannot use 'in' operator to search for '156' 
in [{"id":"1","tagName":"apple"}...

或者还有

Uncaught SyntaxError: Unexpected token k in JSON at position 2

解决方法 Solution :  转换 json字符串 为 JavaScript object， Convert JSON string to JavaScript object

To fix it, converts it to Javascript object via standard JSON.parse() or jQuery $.parseJSON.

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);
});

问题解决！

 PS：

json 字符串不要写成：

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

键名 id 是需要用双引号包裹的！

本文：jQuery: 遍历json字符串, 遍历object数组，报错：Uncaught TypeError: Cannot use ‘in’ operator to search for ‘156’, Uncaught SyntaxError: Unexpected token k in JSON at position 2, loop over JSON string – $.each example