css - How to check if Font Awesome is loaded in web page with javascript? -

i need check if web page has font awesome in it. if not i'm going load javascript. kinda how facebook sdk checks see if there script element containing id "facebook-jssdk", if returns (does nothing), if not loads it. need font awesome.

i think best way check font-awesome, i'm not sure if it's slower loading again if there.

function css(element, property) {   return window.getcomputedstyle(element, null).getpropertyvalue(property); }  window.onload = function () {   var span = document.createelement('span');    span.classname = 'fa';   span.style.display = 'none';   document.body.insertbefore(span, document.body.firstchild);    if ((css(span, 'font-family')) !== 'fontawesome') {     // add local fallback   }   document.body.removechild(span); };