make javascript variable of html value code example

Example 1: html use js variable as text

<h1>"My number: " <span id="myText"></span></h1>

<script>

	//You can use an IIFE (Immediately Invoked Function Expression)
	(() => {
  		var number = "123";
		document.getElementById("myText").innerHTML = number;
	})();
</script>

Example 2: js variable html

<div onload="document.innerHTML(name + ' is ' + age)">