JavaScript Nullish Coalescing(??) Operator

The nullish coalescing (??) operator is used to handle null and undefined values in JavaScript. It allows you to assign a default value when a variable does not have a valid value.

• It returns the right-hand value only when the left-hand value is null or undefined.
• It does not treat 0, false, or empty strings as nullish values.
• It is useful for setting safe default values without overwriting valid data.

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

Syntax:

variable ?? default_value

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

Best Practices

• Use ?? when you only want to handle null or undefined.
• Avoid mixing ?? with || in the same expression without parentheses.
• Prefer ?? for default values in configuration and API responses.