Write a JavaScript program to insert a string at specific position.
<html>
<head>
<title>Insert a string at specific position</title>
</head>
<body>
<script>
var str1 = "Hello World!";
var str2 = "welcome to the ";
var index = 6;
var str3 = insertAt(index, str1, str2);
document.writeln(str3);
function insertAt(pos, s1, s2)
{
var a = s1.substring(0, index);
var b = s1.substring(index, s1.length);
var c = a.concat(s2).concat(b);
return c;
}
</script>
</body>
</html>
