Module to get JSON data with XMLHttpRequest.

getJSON.js

(function() {
    'use strict';

    var getJSON = function( url, callback ) {
        var xhr = new XMLHttpRequest();
        
        xhr.open( 'GET', url );

        xhr.onreadystatechange = function() {
            if( xhr.readyState === 4 && xhr.status === 200 ) {
                var type = xhr.getResponseHeader( 'Content-Type' );

                if( type === 'application/json' ) {
                    callback( JSON.parse( xhr.responseText ) );
                }
            }
        };

        xhr.send( null );
    };

    window.getJSON = getJSON;
}());