Javascript callback function does not work in IE8!

Question

I have a callback function in my open social application which fetches remote date. This works perfect on Chrome and Mozilla browsers but not in IE8. Following is the example for the same, help will be appreciated:

This function: gadgets.io.makeRequest(url, response, params) makes the callback call

and following function process the response:

    function response(obj) { 
      var str = obj.text;        
      var offerDtlPg = str.substr(0, str.length);  
      document.getElementById('pplOfrDetls').innerHTML = offerDtlPg; 
    };