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

In JavaScript, an assignment operator (=) assigns a value to a variable.

Here’s the syntax of the assignment operator:

let a = b;Code language: JavaScript (javascript)

In this syntax, JavaScript evaluates the expression b first and assigns the result to the variable a.

For example, the following 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

The following example uses the += operator to add one to variable x:

let x = 10;
x += 1;
console.log(x); // 11Code language: JavaScript (javascript)

-= operator

The following example uses the -= operator to minus one from the variable x:

let x = 10;
x -= 1;
console.log(x); // 9Code language: JavaScript (javascript)

Output:

9

*= operator

The following example uses the *= operator to multiply 10 with the variable x:

let x = 10;
x *= 10;
console.log(x); // 100Code language: JavaScript (javascript)

/= operator

The following example uses the /= operator to divide x by 2 and assign the result back to x:

let x = 10;
x /= 2;
console.log(x); // 5Code language: JavaScript (javascript)

Output:

5

%= operator

The following example uses the %= operator to get the remainder of x is divided by 2 and assigns the remainder back to x:

let x = 5;
x = x % 2;

console.log(x);Code language: JavaScript (javascript)

Output:

1

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.