JavaScript - Comma & Grouping Operators

Overview

Estimated time: 10–15 minutes

The comma operator evaluates multiple expressions and returns the last. Grouping with parentheses controls precedence.

Learning Objectives

• Use grouping to make precedence explicit.
• Recognize the comma operator and avoid overuse.

Prerequisites

• JavaScript - Delete Operator

Examples

// Grouping
const r = (2 + 3) * 4; // 20

// Comma: evaluate left to right, returns last
let i = 0;
const val = (i += 1, i += 2, i); // i=3, val=3

Common Pitfalls

• Comma operator can hurt readability; prefer separate statements unless truly concise and clear.