JSON Undefined Issues

In IE6 and IE7 browsers or in Ie8-ie10 browser document mode IE7 and below, the console will error: JSON is undefined. This error is normal in IE6 and IE7 browsers, because JSON is supported in the Ie8+ browser. If the ie8+ browser appears, the page is running in IE compatible view. This is usually the case when you can modify DOCTYPE and add x-ua-compatible Meta.

<! DOCTYPE HTML >

<http-equiv= "x-ua-compatible"  content= "Ie=edge"> 

But this approach does not really solve the problem, the correct way is to load the json2.js in your project

Json.parse () and Json.stringify ()--Browser compatibility

Method	Chrome	Firefox	Ie	Opera	Safari
Json.parse ()	Yes	3.5	8.0	10.5	4.0

Reference article:json-js

JSON Undefined Issues