To do basic Maths such as +, -, * in JavaScript, use the Operators. JavaScript includes operators for basic mathematics such as Addition, Subtraction, Multiplication, etc.
Example
You can try to run the following code to learn how to work with basic Maths i.e. Mathematical Operators in JavaScript −
<html>
<body>
<script>
var a = 77;
var b = 30;
var c = "Demo";
var linebreak = "<br />";
document.write("a + b = ");
result = a + b;
document.write(result);
document.write(linebreak);
document.write("a - b = ");
result = a - b;
document.write(result);
document.write(linebreak);
document.write("a / b = ");
result = a / b;
document.write(result);
document.write(linebreak);
document.write("a % b = ");
result = a % b;
document.write(result);
document.write(linebreak);
document.write("a + b + c = ");
result = a + b + c;
document.write(result);
document.write(linebreak);
a = ++a;
document.write("++a = ");
result = ++a;
document.write(result);
document.write(linebreak);
b = --b;
document.write("--b = ");
result = --b;
document.write(result);
document.write(linebreak);
</script>
</body>
</html>