The nullish coalescing operator (??) is a way to set a default value only if the variable is null or undefined.
It is different from the || operator, which treats more values like 0, '', false as “empty.”

Simple Example:

let userName;
let defaultName = 'Guest';

let nameToShow = userName ?? defaultName;
console.log(nameToShow); // Guest

What happens:

userName is undefined.

The ?? operator picks defaultName instead.

Difference from ||

The || operator checks for any falsy value: 0, '', false, null, or undefined.
The ?? operator only checks for null or undefined.

Example:

let points = 0;

console.log(points || 100); // 100 (bad: 0 is treated as falsy)
console.log(points ?? 100); // 0 (good: 0 is kept)

Explanation:

With ||, 0 is treated as “empty” and replaced.

With ??, 0 is considered a valid value and kept.

When to Use (??)

Use ?? when:

You expect 0, false, or '' to be valid values.

You only want to provide a fallback for null or undefined.

This ensures that meaningful values are not accidentally replaced.

Notes

The nullish coalescing operator (??) makes it easy to set safe default values in JavaScript without incorrectly replacing valid data like 0 or false.

It is a clean and powerful tool for handling optional values.