<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script src="12.html" defer ></script>
</head>
<body>
<p id="m1">Text</p>
<hr>
<button onclick="mt()">Click</button>
</body>
</html>
function mt() {
"use strict";
var p;
p = document.getElementById('m1');
p.innerHTML = 'Hello';
}