closures - Passing parameters in Javascript onClick event

Question

I'm trying to pass a parameter in the onclick event. Below is a sample code:

<div id="div"></div>

<script language="javascript" type="text/javascript">
   var div = document.getElementById('div');

   for (var i = 0; i < 10; i++) {
       var link = document.createElement('a');
       link.setAttribute('href', '#');
       link.innerHTML = i + '';
       link.onclick=  function() { onClickLink(i+'');};
       div.appendChild(link);
       div.appendChild(document.createElement('BR'));
       }

   function onClickLink(text) {
       alert('Link ' + text + ' clicked');
       return false;
       }
    </script>

However whenever I click on any of the links the alert always shows 'Link 10 clicked'!

Can anyone tell me what I'm doing wrong?

Thanks

Answer 1

This happens because the i propagates up the scope once the function is invoked. You can avoid this issue using a closure.

for (var i = 0; i < 10; i++) {
   var link = document.createElement('a');
   link.setAttribute('href', '#');
   link.innerHTML = i + '';
   link.onclick = (function() {
      var currentI = i;
      return function() { 
          onClickLink(currentI + '');
      }
   })();
   div.appendChild(link);
   div.appendChild(document.createElement('BR'));
}

Or if you want more concise syntax, I suggest you use Nick Craver's solution.