Bizarre Javascript JSON undefined error

Question

I'm experiencing an error that I haven't been able to find any mention of anywhere. I'm developing an AJAX-enabled WCF web service with ASP.NET. In my ASP.NET master page's , I included the json.js file, copied fresh from json.org. When I run the page, it fails (VS 2008 catches a Javascript exception) on the first line of code in json.js (following lots of comments), which is:

JSON = JSON || {};

The error says that JSON is undefined:

Microsoft JScript runtime error: 'JSON' is undefined

Well, duh! That's why the line is testing if it's defined and if so setting it to an empty object! It is supposed to be undefined, right? Last I heard it was not an error in Javascript to perform such an operation on an undefined variable.

Can anyone give me a clue as to what's going on here? I suspect it's something gone wrong elsewhere that's somehow causing this problem. I don't have deep experience with either Javascript or ASP.NET so it might be that I'm missing some common gotcha in the setup.

Answer 1

You should be using json2.js. The offending line has been changed:

// Create a JSON object only if one does not already exist. We create the
// methods in a closure to avoid creating global variables.

if (!this.JSON) {
    this.JSON = {};
}

Answer 2

As mentioned, you should be using json2.

The error, however, stems from MS handling of global variables. Try window.JSON = window.JSON || {}; From then on, JSON should work just fine.

Answer 3

you might have to do var JSON = JSON || {}; I have run in to similar problems with Javascript in IE8.

Answer 4

I have the same error and i was already using json2;

for me work when i add var

var JSON = JSON || {};