Science Knowings: JavaScript Course For Social Media

Nullish Coalescing Operator

Nullish Coalescing Operator vs Optional Chaining

Before jumping into the Nullish Coalescing Operator, let's recap Optional Chaining, which we explored in the previous session. Optional Chaining allows us to safely access nested properties of an object without worrying about potential 'undefined' values. Now, the Nullish Coalescing Operator takes a different approach to handle null and undefined values.

What is the Nullish Coalescing Operator?

The Nullish Coalescing Operator, denoted by the double question mark (??), is a logical operator that returns the right-hand side operand if the left-hand side operand is null or undefined. Otherwise, it returns the left-hand side operand.

Syntax and Usage

const value = leftOperand ?? rightOperand;

Difference between Null and Undefined

  • null: Represents the intentional absence of a value.
  • undefined: Represents a value that has not yet been assigned or is not available.
  • When to Use the Nullish Coalescing Operator?

    • When you want to assign a default value to a variable if it is null or undefined.
    • When you want to prevent errors caused by accessing non-existent properties.
    • When you want to simplify conditional statements.


    const name = user?.name ?? 'Guest';

    In this example, if the user object has a 'name' property, it will assign the value to the 'name' variable. Otherwise, it will assign the default value 'Guest'.

    Benefits of Using the Nullish Coalescing Operator

    • Improved code readability and maintainability.
    • Reduced need for nested conditional statements.
    • Increased error handling capabilities.

    Code Examples

    const age = user?.age ?? 18;
    const message = result?.message ?? 'No message available';

    Practice Exercises

    Try out some practice exercises to solidify your understanding of the Nullish Coalescing Operator.

    const firstName = user?.firstName ?? 'John';

    In this exercise, assign a default value to the 'firstName' variable if it is null or undefined.


    Test your knowledge of the Nullish Coalescing Operator through a short quiz.


    The Nullish Coalescing Operator provides a convenient way to handle null and undefined values in JavaScript. It simplifies code, improves error handling, and enhances code readability. By understanding and utilizing the Nullish Coalescing Operator effectively, you can write more robust and reliable JavaScript code.

    Next Topic: Array.includes() Method

    In our next session, we will explore the Array.includes() method. This method allows you to check whether a given value exists within an array. We'll cover its syntax, usage, and practical examples to enhance your JavaScript programming skills. Follow us for more JavaScript expertise!