Guest Author - Julie L Baumler

In this article we look at arithmetic operators in JavaScript. Many of the operators are the same as in basic math, so this may seem like a review of elementary school, but some of them may be new to you and it's important to know that you can use them in JavaScript. In the examples below, we mostly use numbers, but in real programs you usually use variables.

Operator	Use	Example	Result
=	assignment	a = 4	a is given the value 4
*	multiplication	3 * 4	12
/	division	12 / 4	3
%	modulus	13 % 4	1
+	addition	3 + 4	7
-	subtraction	12 – 5	7

All of these except for modulus should be familiar to you from elementary school. Modulus (%) gives the remainder from doing integer division. So 13 % 4 means that you divide 13 by 4, this results in 3 with a remainder of 1. Thus 13 % 4 is 1.

You can also use the addition operator with strings. In this case it concatenates (joins) the two strings together. A common mistake is adding (or forgetting) a space between the two strings you are joining.

Operator	Use	Example	Result
+	addition	"he" + "art"	heart
		"he" + " art"	he art

Often you want to add (or subtract, multiply or divide) a variable by some value and then assign the result to the original variable. The assignment operator can be combined with these operators to do this in one step.

Expression	Shortcut
a = a * 3	a *= 3
b = b / 4	a /= 4
c = c % 3	c %= 3
d = d + 5	d += 5
f = f - 2	f -= 2

Happy Scripting!