JavaScript Assignment Operators
Summary: in this tutorial, you will learn how to use JavaScript assignment operators to assign a value to a variable.
Introduction to JavaScript assignment operators
An assignment operator (=) assigns a value to a variable. The syntax of the assignment operator is as follows:
let a = b;Code language: JavaScript (javascript)
In this syntax, JavaScript evaluates the expression b first and assigns the result to the variable a.
The following example declares the counter variable and initializes its value to zero:
let counter = 0;Code language: JavaScript (javascript)
The following example increases the counter variable by one and assigns the result to the counter variable:
let counter = 0;
counter = counter + 1;Code language: JavaScript (javascript)
When evaluating the second statement, JavaScript evaluates the expression on the right hand first (counter + 1) and assigns the result to the counter variable. After the second assignment, the counter variable is 1.
To make the code more concise, you can use the += operator like this:
let counter = 0;
counter += 1;Code language: JavaScript (javascript)
In this syntax, you don’t have to repeat the counter variable twice in the assignment.
The following table illustrates assignment operators that are shorthand for another operator and the assignment:
| Operator | Meaning | Description |
|---|---|---|
a = b | a = b | Assigns the value of b to a. |
a += b | a = a + b | Assigns the result of a plus b to a. |
a -= b | a = a - b | Assigns the result of a minus b to a. |
a *= b | a = a * b | Assigns the result of a times b to a. |
a /= b | a = a / b | Assigns the result of a divided by b to a. |
a %= b | a = a % b | Assigns the result of a modulo b to a. |
a &=b | a = a & b | Assigns the result of a AND b to a. |
a |=b | a = a | b | Assigns the result of a OR b to a. |
a ^=b | a = a ^ b | Assigns the result of a XOR b to a. |
a <<= b | a = a << b | Assigns the result of a shifted left by b to a. |
a >>= b | a = a >> b | Assigns the result of a shifted right (sign preserved) by b to a. |
a >>>= b | a = a >>> b | Assigns the result of a shifted right by b to a. |
Chaining JavaScript assignment operators
If you want to assign a single value to multiple variables, you can chain the assignment operators. For example:
let a = 10, b = 20, c = 30;
a = b = c; // all variables are 30Code language: JavaScript (javascript)
In this example, JavaScript evaluates from right to left. Therefore, it does the following:
let a = 10, b = 20, c = 30;b = c; // b is 30
a = b; // a is also 30
Code language: JavaScript (javascript)
Summary
- Use the assignment operator (
=) to assign a value to a variable. - Chain the assignment operators if you want to assign a single value to multiple variables.