JavaScript Operators

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Learn how JavaScript operators combine expressions into more complex ones, from binary operators like addition to unary operators and the ternary operator.

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Operators allow you to get one or more simple expressions and combine them to form a more complex expression.

Take this line:

const total = price * quantity

Here * is an operator. The values it works on, price and quantity, are called operands. The operator takes those two operands and produces a new value.

We can classify operators based on the number of operands they work with.

Binary operators

Most operators work with 2 operands. We call them binary operators:

They don’t all produce numbers. Comparison and equality operators produce a boolean:

const age = 18
age >= 18 // true

And that boolean is what you use in if statements and loops.

Unary operators

Some operators work with a single operand. We call them unary operators:

For example, ! flips a boolean:

const loggedIn = false
!loggedIn // true

And typeof tells you the type of a value:

typeof 'flavio' // 'string'

The ternary operator

Just one operator works with 3 operands: the ternary operator. It’s a compact way to pick between two values based on a condition:

const age = 18
const status = age >= 18 ? 'adult' : 'minor'

Be careful with precedence

When you combine multiple operators in one expression, JavaScript applies them in a fixed order. Multiplication runs before addition, like in math:

2 + 3 * 4 // 14, not 20

My advice is to not memorize the precedence rules. Use parentheses to make the order explicit:

(2 + 3) * 4 // 20

Anyone reading the code (including you, in six months) will thank you.

Tagged: JavaScript · All topics
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