I generate the set of buttons within html table as follows and then I want to call to function when it click.
$.each(childData, function(key, item) {
va
Delegate the event to static parent:
$(div).on("click", ".download", function(){
Here div can be the static parent which was available when page was loaded at first load. Although document or body can also be used in place of div.
As you have not presented how you create div element but one thing has to be noticed that you are generating an invalid markup. As a td element can't be a child of div but table's tr.