<html>
<script type = "text/javascript">
function function1()
{
var string1 = "First string";
var string2 = "Second string";
var string3 = string1.concat(string2);
document.getElementById("str").innerHTML = "concatenated string" + string3;
}
</script>
<body>
<div id="str"></div>
<button onClick = "function1()">Click here</button>
</body>
</html>