Code Comments

Before we get too far, we need to learn how to add comments. A comment is a note to the developer. It is text within the source code that we do not want the computer to interpret. Every programming language has a concept of code comments, but the syntax required to denote a comment and set it apart from the rest of the source code is different in each programming language.

Syntax

In HTML, we indicate that a line of text is a comment like this:

<!-- This sentence will not appear to the user. -->

The special opening tag <!-- marks the start of the text to be ignored by the computer, and ends with -->.

Comments can last for several lines:

<!-- This sentence will not appear to the user.
Nor will this.
Or this.
-->

Bonus: Disabling Code

The other main purpose of code comments is to temporary disable some HTML code, perhaps as part of a debugging strategy:

<h1>Hello!</h1>

<!-- <a href="http://www.google.com">Search</a> -->

<h2>Goodbye!</h2>

Try that in your browser to confirm which code will be interpreted and which will not.

Bonus Bonus: Keyboard Shortcut

Using comments to temporarily disable a line of code is so common, you'll want to do it often.

In Atom, you can use the menu option Edit | Toggle Comments. But hopefully you'll be using this technique so much that the keyboard shortcut will become second nature, Cmd / (on Windows, CTRL /).