97 lines
3.0 KiB
Markdown
97 lines
3.0 KiB
Markdown
---
|
|
title: Comments
|
|
---
|
|
|
|
## Comments
|
|
|
|
Programmers use comments to add hints, notes, suggestions, or warnings to their source code; they have no effect on the actual output of the code. Comments can be very helpful in explaining the intent of what your code is or should be doing.
|
|
|
|
It is always best practice when starting out to comment more often than not, as it can help those reading your code to understand what exactly your code is intending to do.
|
|
|
|
JavaScript has two ways of assigning comments in its code.
|
|
|
|
The first way is the `//` comment; all text following `//` on the same line is considered as a comment. For example:
|
|
|
|
```javascript
|
|
function hello() {
|
|
// This is a one line JavaScript comment
|
|
console.log("Hello world!");
|
|
}
|
|
hello();
|
|
```
|
|
|
|
The second way is the `/* */` comment, which can be used for both single-line and multi-line comments. For example:
|
|
|
|
```javascript
|
|
function hello() {
|
|
/* This is a one line JavaScript comment */
|
|
console.log("Hello world!");
|
|
}
|
|
hello();
|
|
```
|
|
|
|
```javascript
|
|
function hello() {
|
|
/* This comment spans multiple lines. Notice
|
|
that we don't need to end the comment until we're done. */
|
|
console.log("Hello world!");
|
|
}
|
|
hello();
|
|
```
|
|
The third way is the `/** */` comment, a format popularly known as JSDoc, can be used to clearly describe functions, classes, methods, and variables in your codebase in a detailed way. For example:
|
|
|
|
```javascript
|
|
/**
|
|
* Adds two numbers together
|
|
*
|
|
* @param {number} num1 - first parameter
|
|
* @param {number} num2 - second parameter
|
|
* @returns {number}
|
|
*/
|
|
function addTwoNumbers(num1, num2) {
|
|
return num1 + num2;
|
|
}
|
|
console.log(addTwoNumbers(10,20)) // will print 30 in the console.
|
|
|
|
You can also prevent execution of Javascript code just commenting the code lines like this:
|
|
```javascript
|
|
function hello() {
|
|
/*console.log("Hello world!");*/
|
|
}
|
|
hello();
|
|
```
|
|
#### More Information:
|
|
<a href='https://www.digitalocean.com/community/tutorials/how-to-write-comments-in-javascript' target='_blank' rel='nofollow'>How To Write Comments in JavaScript</a>
|
|
<h3>Many IDEs come with a keyboard shortcut to comment out lines. </h3>
|
|
<ol>
|
|
<li>Highlight text to be commented</li>
|
|
<li>Mac: Push Command(Apple Key) & "/"</li>
|
|
<li>Windows: Push Control & "/"</li>
|
|
<li>You can also uncomment code by doing the same steps</li>
|
|
</ol>
|
|
A shortcut to comment out a section of javascript in many code editors is to highlight the lines of code you want to comment out, then press `Cmd/Ctrl + /`.
|
|
|
|
Comments are also very helpful for code testing as you can prevent a certain code-line/block from running
|
|
|
|
```javascript
|
|
function hello() {
|
|
// The statement below is not going to get executed
|
|
// console.log('hi')
|
|
}
|
|
hello();
|
|
```
|
|
|
|
```
|
|
function hello() {
|
|
// The statements below are not going to get executed
|
|
/*
|
|
console.log('hi');
|
|
console.log('code-test');
|
|
*/
|
|
}
|
|
hello();
|
|
```
|
|
|
|
#### More Information:
|
|
* <a href='https://www.digitalocean.com/community/tutorials/how-to-write-comments-in-javascript' target='_blank' rel='nofollow'>How To Write Comments in JavaScript</a>
|