How to add string function exactly?

Question

I created a code with Javascript: https://code.sololearn.com/WK36M9gkTNY8/#
I cannot understand how to correct the length function.
Please help me if you can.

Answer 1

use name.length

Answer 2

var name=prompt("please enter your name","");
var letters=name.length;
alert("Your name has "+letters+" letters")

Answer 3

Thanks guys it is working absolutely perfectly.
Thank you for your support.