MSIE and addEventListener Problem in Javascript?

Question

document.getElementById('container').addEventListener('copy',beforecopy,false );

In Chrome / Safari, the above will run the "beforecopy" function when the content on the page is being copied. MSIE is supposed to support this functionality as well, but for some reason I'm getting this error:

"Object doesn't support this property or method"

Now, it's my understanding that Internet Explorer won't play with the body node, but I would have thought providing a node by ID would work fine. Does anyone have any ideas about what I'm doing wrong? Thanks in advance.

** Bonus points for anyone who can tell me what the 3rd parameter "False" is good for.

Answer 1

In IE you have to use attachEvent rather than the standard addEventListener.

A common practice is to check if the addEventListener method is available and use it, otherwise use attachEvent:

if (el.addEventListener){
  el.addEventListener('click', modifyText, false); 
} else if (el.attachEvent){
  el.attachEvent('onclick', modifyText);
}

You can make a function to do it:

function bindEvent(el, eventName, eventHandler) {
  if (el.addEventListener){
    el.addEventListener(eventName, eventHandler, false); 
  } else if (el.attachEvent){
    el.attachEvent('on'+eventName, eventHandler);
  }
}
// ...
bindEvent(document.getElementById('myElement'), 'click', function () {
  alert('element clicked');
});

You can run an example of the above code here.

The third argument of addEventListener is useCapture; if true, it indicates that the user wishes to initiate event capturing.