JSFiddle - React, Tailwind, and code Playground

HTML

<p id="log"></p>

JavaScript

var log = document.getElementById('log');

var testString = 'var test1 = 1; var test1=1; var test-test=1 var test_3=3;';

var newString = testString.replace(/var ([a-zA-Z0-9_-]{1,})/g, function (match) {
	log.innerHTML += match + '<br/>';
	return match;
});