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1-js/01-getting-started/03-comments/article.md

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+
+# Comments
+
+As time goes on, scripts tend to become more complex. We can add *comments* to describe what the code does and why.
+
+Comments can be put into any place of a script. They don't affect its execution because the engine simply ignores them.
+
+**One-line comments start with two forward slash characters `//`. The rest of the line is a comment.**
+
+Such comment may occupy a full line of its own or follow a statement.
+
+Like here:
+```js run
+// This comment occupies a line of its own
+console.log("Hello");
+
+console.log("World"); // This comment follows the statement
+```
+
+For longer, descriptive comments that span multiple lines, we can use the `/* ... */` syntax.
+
+**Multiline comments start with a forward slash and an asterisk <code>/&#42;</code> and end with an asterisk and a forward slash <code>&#42;/</code>.**
+
+Like this:
+
+```js run
+/* An example with two messages.
+This is a multiline comment.
+*/
+console.log("Hello");
+console.log("World");
+```
+
+The content of comments is ignored, so if we wrap a piece of code into `/* ... */`, it won't execute.
+
+It can be handy to temporarily disable ("comment out") a part of code:
+
+```js run
+/* Commenting out the code
+console.log("Hello");
+*/
+console.log("World");
+```
+
+```smart header="Use hotkeys!"
+In most editors, a line of code can be commented out by pressing the `key:Ctrl+/` hotkey for a single-line comment and something like `key:Ctrl+Shift+/` -- for multiline comments (select a piece of code and press the hotkey). 
+
+For Mac, try `key:Cmd` instead of `key:Ctrl` and `key:Option` instead of `key:Shift`.
+```
+
+````warn header="Nested comments are not supported!"
+There may not be `/*...*/` inside another `/*...*/`.
+
+Such code will die with an error:
+
+```js run no-beautify
+/*
+  /* nested comment leads to an error! */
+*/
+console.log( "World" );
+```
+````
+
+Please, don't hesitate to comment your code.
+
+Comments increase the overall code footprint, but that's not a problem at all. There are many tools which minify code before publishing to a production server. They remove comments, so they don't appear in the working scripts. Therefore, comments do not have negative effects on production at all.