JavaScript Nullish Coalescing(??) Operator

Last Updated : 10 Jun, 2024

The nullish coalescing (??) operator is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined, and otherwise returns its left-hand side operand. It's commonly used to provide default values for variables.

Syntax:

variable ?? default_value

Below are examples of the Nullish Coalescing Operator.

Example 1: In this example, we will see a basic function using the nullish coalescing operator

javascript

function foo(bar) { 
    bar = bar ?? 55; 
    console.log(bar); 
} 
foo(); // 55 
foo(22); // 22

Output

55
22

Example 2: The more common use case is to set default values for JSON objects as follows.

javascript

const foo = { 
    bar: 0 
} 

const valueBar = foo.bar ?? 42; 
const valueBaz = foo.baz ?? 42; 

// Value of bar: 0 
console.log("Value of bar: ", valueBar); 

// Value of bar: 42 
console.log("Value of baz: ", valueBaz);

Output

Value of bar:  0
Value of baz:  42

Supported Browsers: The browsers supported by JavaScript Nullish Coalescing Operator are listed below:

JavaScript Nullish Coalescing(??) Operator

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JavaScript Nullish Coalescing(??) Operator

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