@SamPopes answer from this thread is compatible with IE7+, Firefox and Chrome. I have edited his code so that you can pass your table as a function parameter, as I dynamically create my table via. document.createElemet('table').
function export(obj) {
  var tab_text="<table border='2px'><tr>";
  var textRange; var j=0;
  tab = obj; //Table
  for(j = 0 ; j < tab.rows.length ; j++){     
    tab_text=tab_text+tab.rows[j].innerHTML+"</tr>";
    //tab_text=tab_text+"</tr>";
  }
  tab_text=tab_text+"</table>";
  tab_text= tab_text.replace(/<A[^>]*>|<\/A>/g, "");//remove if you want links in your table
  tab_text= tab_text.replace(/<img[^>]*>/gi,""); // remove if you want images in your table
  tab_text= tab_text.replace(/<input[^>]*>|<\/input>/gi, ""); // removes input params
  var ua = window.navigator.userAgent;
  var msie = ua.indexOf("MSIE "); 
  if (msie > 0 || !!navigator.userAgent.match(/Trident.*rv\:11\./))      // If Internet Explorer
    {
      txtArea1.document.open("txt/html","replace");
      txtArea1.document.write(tab_text);
      txtArea1.document.close();
      txtArea1.focus(); 
      sa=txtArea1.document.execCommand("SaveAs",true,"export.xls");
  } else { //other browser not tested on IE 11
      sa = window.open('data:application/vnd.ms-excel,' + encodeURIComponent(tab_text));            
      return (sa);
  }
}