Logical Assignment Operators in JavaScript: Small Syntax, Big Wins

JavaScript developers often write repetitive conditional logic when assigning default values or updating state based on truthiness. This post introduces the ES2021 logical assignment operators—||=, &&=, and ??=—which combine a logical operator with assignment to streamline these patterns and make code more readable and intentional.

The author breaks down each operator:

- ||= assigns the right-hand value if the left-hand side is falsy.

• &&= updates the left-hand side only when it’s truthy.
• ??= assigns only if the left-hand side is null or undefined, preserving falsy-but-valid values like 0, false, or "".

Support for these operators is solid across modern platforms—Chrome, Firefox, Safari, Edge, and Node.js versions 15+—though they are not available in Internet Explorer. The post also warns against using optional chaining (?.) on the left-hand side of these expressions, as that usage is not valid syntax. Overall, the operators offer concise syntax with real-world benefits for prop defaults, config management, and frontend state mutation workflows.