JavaScript Comments: Syntax, JSDoc Documentation & Clean Code Practices

Comments are non-executable explanatory notes written directly within source code. The JavaScript engine completely ignores comments during compilation and execution. When utilized effectively, comments transform complex codebases into readable, maintainable, and self-explanatory software systems.

Types of Comments in JavaScript

JavaScript provides two native syntax forms for commenting code:

1. Single-Line Comments (//)

Used for brief inline explanations or quick single-line notes. Everything from the double slash to the end of that specific physical line is ignored:

// Calculate student final grade based on theory and lab practicals
const totalScore = theoryMarks + practicalMarks; // Inline note

2. Multi-Line Comments (/* ... */)

Used for extensive conceptual descriptions, licensing headers, or temporarily commenting out large blocks of code during debugging:

/*
 * Algorithm: Binary Search Implementation
 * Time Complexity: O(log N)
 * Prerequisites: Array must be sorted in ascending order
 */
function binarySearch(arr, target) {
    let left = 0;
    let right = arr.length - 1;
    // ... search logic
}

Professional Enterprise Standard: JSDoc Annotations

JSDoc is the industry standard for documenting JavaScript functions, classes, and APIs. Modern editors like VS Code parse JSDoc annotations to provide rich autocomplete tooltips and static type safety warnings:

/**
 * Calculates the compounded interest on a financial investment.
 * 
 * @param {number} principal - The initial capital invested in INR.
 * @param {number} rate - Annual interest rate (percentage, e.g. 7.5).
 * @param {number} years - Duration of investment in whole years.
 * @returns {number} The total compounded amount formatted to 2 decimals.
 * @throws {Error} Throws error if principal or years are negative.
 */
function calculateCompoundInterest(principal, rate, years) {
    if (principal < 0 || years < 0) {
        throw new Error("Financial values cannot be negative.");
    }
    const amount = principal * Math.pow((1 + (rate / 100)), years);
    return Number(amount.toFixed(2));
}

Clean Code: Commenting Best Practices vs. Antipatterns