javascript encapsulates the method of addLoadEvent to realize page loading and executing multiple functions at the same time

In this paper, an example of javascript encapsulation addLoadEvent implementation page loading and executing multiple functions at the same time. Share it for your reference, as follows:

If you want to execute multiple functions at the same time, you can put them into an array, then loop the array and execute it in the onload event, or use another convenient function, addLoadEvent:

function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
   } else {
    window.onload = function() {
         if (oldonload) {
          oldonload();
         }
      func();
    }
   }
 }

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