cannot get json.parser work on my ie8

I've been looking at this a very long time time. My script works on chrome, firefox, safari except for IE 8. Everybody uses IE8 so I cannot say my program is working. I couldn't to figure out what the problem is. Here is my code:Is there an easy way to get the json.parser work for IE8. Man this is really frustrating.

$(document).ready(function() {
var myDate;
 function request_cpu_Data() {
     $.ajax({
         url: 'get_cpu.php',
         success: function(data) {
        var myObj = JSON.parse(data); 
        var point = cpu_chart.series[0].points[0];
        var newVal=myObj[1];
        myDate=myObj[0];
        point.update(newVal); 
        setTimeout(request_cpu_Data, 1000);
        },
        cache: false
  
    });
}