How to change the url address of a button link using js?

Question

JavaScript

There is one button with a link to the page, how to change it through js? tried like this
Tried to give id to link : a id ="gotopay"
then in js

document.getElementById('gotopay').href ="http://site.ru/id=2"

but not working

Answer 1

but not working

Actually works: jsfiddle.net/bujvd9yr