JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="ga" value="UA-12345-12" placeholder="Enter Google Analytics ID" />

JavaScript

function validateGA(id) {
    var regexp = /ua-\d+-\w\d+/;
    return regexp.test(id);
}

var ga = document.getElementById('ga').value;

console.log(validateGA(ga));