Nullish Coalescing Assignment Operator in JavaScript

Streamlining Default Value Assignments: The Power of Nullish Coalescing Operator in JavaScript

Nullish Coalescing Assignment Operator in JavaScript

In JavaScript, dealing with potentially undefined or null values has been a long-standing challenge for developers. We’ve previously explored the Nullish Coalescing Operator (??), a handy tool for selecting default values when encountering null or undefined variables. Building upon this, JavaScript introduced the Nullish Coalescing Assignment Operator (??=), a powerful addition to simplify default value assignments. Let's dive deeper into this operator, its functionality, and how it enhances JavaScript code.

Introducing the Nullish Coalescing Assignment Operator (??=)

The Nullish Coalescing Assignment Operator (??=) is a fusion of the Nullish Coalescing Operator (??) and the assignment operator (=). It provides a succinct way to assign a default value to a variable only if the variable is null or undefined.

let myVar;
myVar ??= 'random';
console.log(myVar); // Output: 'random'

myVar = 'existingValue';
myVar ??= 'default';
console.log(myVar); // Output: 'existingValue'

In the first example, myVar is assigned the default value 'default' because it was initially undefined. However, in the second example, since myVar already holds a value ('existingValue'), the default value is not assigned.

Benefits of the Nullish Coalescing Assignment Operator

  1. Clarity and Readability: The ??= operator clearly conveys the intention of assigning a default value only when necessary. It enhances code readability by succinctly handling null or undefined variables.

  2. Prevents Unintended Side Effects: By strictly checking for nullish values, the operator prevents unintended overwriting of existing values with defaults. It ensures that default assignments occur only when variables are truly null or undefined.

  3. Conciseness: With the ??= operator, developers can achieve default value assignments with fewer lines of code compared to traditional conditional statements. This promotes code conciseness and improves overall code maintainability.


The Nullish Coalescing Assignment Operator (??=) is a valuable addition to JavaScript's toolkit, providing a streamlined approach to handling default value assignments. Its simplicity, clarity, and effectiveness make it a powerful tool for developers, enabling them to write cleaner and more maintainable code. As JavaScript evolves, leveraging features like ??= empowers developers to write efficient and robust applications.

Incorporating the Nullish Coalescing Assignment Operator into your JavaScript codebase can enhance code readability and streamline default value assignments. So next time you encounter scenarios requiring default values, consider using ??= for a more concise and elegant solution.