Assignment operators

Learn shortcut assignments with =, +=, -=, *=, /= and ++/--.

Assignment operators

The assignment operator = gives a value to a variable. For example, let x = 5. x now holds 5.

Compound assignment combines operation and assignment: x += 3 is the same as x = x + 3. Similarly there are -=, *=, /=, %=.

This shortens long expressions. Especially when updating a counter, count += 1 is common.

Increment and decrement

The increment and decrement operators are written with ++ and --. They increase or decrease a variable's value by 1.

For example, after let count = 5; count++;, count becomes 6. The same can be done with count += 1; both give the same result.

There is a small difference between ++count (prefix) and count++ (postfix): prefix increments then returns the value, postfix returns the value then increments. The difference does not matter when used alone.

Exercise Calculate with compound assignment

Declare let total = 100. Add 20 with total += 20, then subtract 10 with total -= 10, then double with total *= 2. Finally call console.log(total).

Show example solution

let total = 100;
total += 20;
total -= 10;
total *= 2;
console.log(total);

Test yourself

Compound assignment

let count = 5;
count ____ 2;

Show answer

let count = 5;
count += 2;

Match the assignment types

=

Assignment
+=

Add and assign
-=

Subtract and assign
++

Increment by one
What does x++ do?
- Adds 1 to x
- Adds 2 to x
- Decrements x by one
- Resets x
Show answer

Adds 1 to x — The correct answer: adds 1 to x. The ++ operator increments by 1.

Next lesson: Comparison operators

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