Assignment operators
Learn shortcut assignments with =, +=, -=, ++ and --.
The assignment operator =
To give a variable a value, you use the = operator. It takes the value on the right and stores it in the variable on the left. For example, let score = 90; makes score hold 90.
Assignment is not one-time; you can give the same variable a new value later: score = 85;. The let keyword is used only for the first declaration, not for later updates.
Compound assignment
When you update a variable, you can avoid writing it twice by using a compound assignment operator. score += 5 means the same as score = score + 5; it is just shorter.
Likewise -=, *=, /= and %= work. Most updates end up in this compact form. Also ++ adds one and -- subtracts one.
Exercise Update the stock counter
Declare stock with an initial value of 20. Then add 5 using the += operator.
Show example solution
// Declare and update the stock variable
let stock = 20;
stock += 5;Test yourself
-
What does count += 3 do?
let count = 10; count += 3; console.log(count);- Adds 3 to count (becomes 13)
- Sets count to 3
- Sets count to 30
- Throws an error
Show answer
Adds 3 to count (becomes 13) — Correct. The += operator adds the right side to the current value; count becomes 10 + 3 = 13.
-
Increment the counter by one
let visits = 7; visits____; console.log(visits);Show answer
let visits = 7; visits++; console.log(visits); -
Match the assignment operator
- =
- Assign a value
- +=
- Add and assign
- -=
- Subtract and assign
- ++
- Increment by one