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;Copy

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;Copy

The following example increases the counter variable by one and assigns the result to the counter variable:

let counter = 0;
counter = counter + 1;Copy

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;Copy

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); // 11Copy

-= operator #

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

let x = 10;
x -= 1;
console.log(x); // 9Copy

Output:

9Copy

*= operator #

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

let x = 10;
x *= 10;
console.log(x); // 100Copy

/= 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); // 5Copy

Output:

5Copy

%= 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);Copy

Output:

1Copy

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 30Copy

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 30Copy

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.