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

Question

I need to check if a web page has Font Awesome in it. If not I'm going to load it with javascript. Kinda like how the facebook sdk checks to see if there is a script element containing the id "facebook-jssdk", if so it just returns (does nothing), if not it loads it. I need to do that for Font Awesome.

Answer 1

I think this is the best way to check for font-awesome, but I'm not sure if it's slower then just loading it again even if it is 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 a local fallback
  }
  document.body.removeChild(span);
};