Look at the program hello.js again from the section Your first program. Notice the funny line /** @param {NS} ns */? It is one of various ways that JavaScript allows you to insert a comment in your code. You start a comment with the comment opener /** and end the comment with the comment closer */. When the script hello.js runs, everything between /** and */ will be ignored. You could also have written the comment of hello.js as follows:

hello-doc-multiline.js

/**
 * Greetings.
 *
 * @param {NS} ns The Netscript API.
 */
export async function main(ns) {
    ns.tprint("Hello, world!");
}

What’s that funny {NS}? Do not worry about it for now. We will discuss it later in the tutorial, in the chapter Put that in a function. You can also write the comment like this:

hello-doc-line.js

// Greetings.
//
// @param {NS} ns The Netscript API.
export async function main(ns) {
    ns.tprint("Hello, world!");
}

The comment pattern /** <comment goes here> */ is ideal for multiline comments. Use this pattern to explain the purpose of a block of code. The comment pattern // <comment goes here> is often used for a one-line comment, a short description of a line or block of code. The program below illustrates the use of the multiline and one-line documentation styles.

greet.js

/**
 * More greetings.
 *
 * @param {NS} ns The Netscript API.
 */
export async function main(ns) {
    // Some greetings.
    ns.tprint("Hello!"); // Salutation.
    ns.tprint("How are you today?"); // Friendly question.
}

If a computer is going to ignore comments, why would you bother to insert comments in your script? The usual reason is documentation. A computer executes your JavaScript code, but it is a human (most probably yourself) who would be reading and trying to understand the code at some future time. You write code not just for a computer, but for other humans as well. Imagine you are trying to solve a programming problem. You struggle for a few hours, maybe a few days or weeks. After a while, you find a clever solution and write up the solution as JavaScript code. The code works and outputs the correct result. You move on to another problem or some other challenge. Some time passed, probably a few weeks or months. You come back to the code for the clever solution and have forgotten how or why the code works. Reading the code gives you some hints, but you still struggle to remember the name of the technique you used. If only you had written at least a one-line comment to explain the technique. The situation is contrived, absolutely. The message is clear: document your code. Even if it is a one-line comment, use that single line to note the name of the (tricky or clever) technique the code is implementing.