add two numbers javascript

JavaScript
let a = 4;
let b = 5;
document.write(a + b);return a+b;//use parseFloat(x); to change string to number
a=10;
b=20;
console.log(parseFloat(a)+parseFloat(b));//this will give a+b=30
//while
consle.log(a+b); //will give a+b=1020 [as String]<!--Add two integer numbers using JavaScript.-->
<html>
	<head>
		<title>Add two integer numbers using JavaScript.</title>
		<script type="text/javascript">
			function addTwoNumbers(textBox1, textBox2){
				var x=document.getElementById(textBox1).value;
				var y=document.getElementById(textBox2).value;
				var sum=0;
				sum=Number(x)+Number(y);
				alert("SUM is: " + sum);
			}
		</script>
	</head>
<body>
	<h1>Add two integer numbers using JavaScript.</h1>
	<b>Enter first Number: </b><br>
	<input type="text" id="textIn1"/><br>
	<b>Enter second Number: </b><br>
	<input type="text" id="textIn2"/><br><br>
	<input type="button" id="btnSum" value="Calculate SUM" onClick="addTwoNumbers('textIn1','textIn2')"/>
</body>

</html>
var x = 2 + 3;
//x = 5
Source

Also in JavaScript: