Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <body> <p id="demo">Click the button to locate where in the string a specifed value occurs.</p> <button onclick="myFunction()">Try it</button> <script> function myFunction() { var str="Hello world, welcome to the universe."; var n=str.indexOf("welcome"); document.getElementById("demo").innerHTML=n; } </script> </body> </html>
Result:
W3Schools.com - Try it yourself