faith solution: modular javascript approach and event binding

simple adding application using modular javascript and html
<html>
<body>
<input type="text" id="t1">
<input type="text" id="t2">
<input type="button" id="b1" value="Add">
<script type="text/javascript" src="module1.js">

</script>
</body>

</html>
script file
"use strict";
var obj=(function()
{
obj={};
obj.add=function()
{
var n1=parseInt(document.getElementById("t1").value);
var n2=parseInt(document.getElementById("t2").value);
var sum=n1+n2;
alert(sum);
};
return obj;
}());

//document.getElementById("b1").addEventlistner("click",obj.add);
document.getElementById("b1").onclick=obj.add;

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modular javascript approach and event binding