Make JavaScript specific code work in IE7

Question

This code works in modern browsers - but is not working in the IE7. Can someone help me where the problem lies:

function makePay() {
            var obj = {
                            'product' : 'speakers',
                            'paid' : 300,
                            'toBePaid' : 560,
                            'paymentsLeft' : 3,
            }              

            return (obj.toBePaid - obj.paid) / obj.paymentsLeft;
}

var btn = document.getElementById("result");
btn.addEventListener("click", function(){
            alert(makePay());
}, false);

What's this boom of asking about [legacy IE eventhandling](https://msdn.microsoft.com/en-us/library/ie/ms536343%28v=vs.85%29.aspx)? — Teemu, Jan 29 '15 at 19:32
We handle IE7 at work because many of our clients in the government are forced to use it. So handling legacy is a moot point for some people. Or it's a school project requirement. — Sterling Archer, Jan 29 '15 at 19:35
@adeneo Well, nobody supports old IE versions voluntarily. So “stop supporting IE 7” is not very helpful here :-) — aaronk6, Jan 29 '15 at 19:35

score 2 · Answer 1 · edited May 23 '17 at 11:57

The reason for IE 7 failing is the addEventListener method.

IE versions older than 9 have their own, proprietary method for attaching event handlers. You’ll need to check if addEventListener is supported and if it’s not the case, check for attachEvent and use this instead.

Example (taken from https://stackoverflow.com/a/6927800/1387396):

function addEvent(evnt, elem, func) {
   if (elem.addEventListener)  // W3C DOM
      elem.addEventListener(evnt,func,false);
   else if (elem.attachEvent) { // IE DOM
      elem.attachEvent("on"+evnt, func);
   }
   else { // No much to do
      elem[evnt] = func;
   }
}

Good luck! I feel with you.

Make JavaScript specific code work in IE7

1 Answers1