<!DOCTYPE html>
<html>
<body>
<p id="p1">Please locate where 'locate' occurs!.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var str = document.getElementById("p1").innerHTML;
var pos = str.indexOf("locate");
document.getElementById("demo").innerHTML = pos;
}
</script>
</body>
</html>