What Is JavaScript Double Question Mark?

The JavaScript double question mark, also known as the "null coalescing operator", is a brand new feature in JavaScript released in the 2023 version. It's a much-needed tool that allows developers to write shorter, cleaner, and more efficient code when working with null values. In this article, we'll explain what it does and how to use it.

What Does It Do?

The double question mark is a binary operator that returns the value of the first operand if it exists and is not null, and the second operand if the first one is null or undefined. This means that if the first value is not null, it will be returned, and if it is null, the second value will be returned. This can be used to simplify if-else statements, and make code faster and more efficient.

Example Code

Let's look at an example of JavaScript double question mark in action. In this example, we have a variable called "name", which may or may not be null. We want to assign it a value of either "John" or "Unknown" depending on whether it is null or not.

Without the double question mark, you would have to write an if-else statement to achieve this:

let name;
 
 if (name !== null) {
 name ="John";
 } else {
 name ="Unknown";
 }

But with the double question mark, you can do it in a single line:

let name = name ?? "Unknown";

More Uses

The double question mark can also be used to replace the ternary operator (?:) when working with null values. For example, you can replace this code:

let name = (name !== null) ? "John" : "Unknown";

With this code:

let name = name ?? "Unknown";

Conclusion

The JavaScript double question mark is a powerful new tool that allows developers to write cleaner, more efficient code. It can be used to replace traditional if-else statements and ternary operators, and make code faster and easier to read. If you're working with null values in JavaScript, this is a must-have tool.