How to Addition Assignment or += Operator in JavaScript

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Muhammad Muzammil Hussain Feb 02, 2024
JavaScript JavaScript Operators
  1. What Is += in JavaScript
  2. Use the -= as a Subtraction Assignment Operator
  3. Use the *= as a Multiplication Assignment Operator
  4. Use the /= as a Division Assignment Operator
  5. Use the %= as a Remainder/Modulus Assignment Operator
How to Addition Assignment or += Operator in JavaScript

This article will inform you about JavaScript’s addition assignment operator. Let’s look at how it works and read the other assignment operators.

What Is += in JavaScript

The += is the addition assignment operator in JavaScript. It adds two values together and assigns the result to a variable in a single JavaScript statement.

Syntax:

x += y;
means x = x + y;
a += b;
means a = a + b;

The behavior of the addition assignment operator, either addition or concatenation, depends on the types of two operands, as explained in the following example.

<html>
    <head>
        <title>
            JavaScript addition assignment operator
        </title>
    </head>
    <body>
        <h3> <u> JavaScript addition assignment operator </u></h3>
    <body>
        <script>
            var a = 3;
            var b = "Delft"
            document.write(a += 5); // Addition
            document.write("<br>");
            document.write("<br>");
            document.write(b += "Stack"); // Concatenation
        </script>
</html>

Output:

JavaScript addition assignment operator
8
DelftStack

Example of JavaScript addition assignment operator:

<html>
    <head>
        <title>
            JavaScript addition assignment operator
        </title>
    </head>
    <body>
        <h3> <u> JavaScript addition assignment operator in different scenarios </u></h3>
    <body>
    <script>
        var  ds = 'DelftStack';
        var n = 4;
        var  b = true;

        // adding number with number results in addition
        document.write(n += 5);  // 9
        document.write("<br>");

        // adding Boolean with Number results in addition
        document.write(b += 1); // 2
        document.write("<br>");

        // adding Boolean with Boolean results in addition
        document.write(b += false); // 2
        document.write("<br>");

        // adding Number with String results in concatenation
        document.write(n += 'Cybexo') // "9Cybexo"
        document.write("<br>");

        // adding String with Boolean results in concatenation
        document.write(ds += false) // "DelftStackfalse"
        document.write("<br>");

        // adding String with String results in concatenation
        document.write(ds += ' Technology') // "DelftStack Technology"
    </script>
</html>

Output:

JavaScript addition assignment operator in different scenarios
9
2
2
9Cybexo
DelftStackfalse
DelftStackfalse Technology

Similarly, in JavaScript, we also have:

  • Subtraction assignment operator -=
  • Multiplication assignment operator *=
  • Division assignment operator /=
  • Modulus assignment operator %=

Use the -= as a Subtraction Assignment Operator

The subtraction assignment operator is used to subtract the right operand number value from a variable value and then assign the result to the variable.

Syntax:

x -= y;
means x = x - y;
a -= b;
means a = a - b;

Use the *= as a Multiplication Assignment Operator

The multiplication assignment operator multiplies a variable by the value of the right operand and then assigns the result to the variable in a single statement.

Syntax:

x *= y;
means x = x * y;
a *= b;
means a = a * b;

Use the /= as a Division Assignment Operator

It divides the variable by the right operand number and assigns the result to the variable in a single JavaScript statement.

Syntax:

x /= y;
means x = x / y;
a /= b;
means a = a / b;

Use the %= as a Remainder/Modulus Assignment Operator

The remainder/modulus assignment operator divides a variable by the value of the right operand and then assigns the remainder to the variable in a single JavaScript statement.

Syntax:

x %= y means x = x % y
a %= b means a = a % b