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function load(src, callbackSuccess, callbackError) {
  var head   = (document.getElementsByTagName('head') || [])[0] || null;
      
  if(head) {
    var script = document.createElement('script');
    
    script.type  = 'application/javascript';
    script.src   = src;
    script.async = true;
    
    script.onload  = callbackSuccess;
    script.onerror = callbackError;
    script.onreadystatechange = function() {
      if(script.readyState === 'loaded' || script.readyState === 'complete') {
        script.onreadystatechange = null;
        
        callbackSuccess();
      }
    }
    
    head.appendChild(script);
  }
}