One last thing for this chapter: comments. Inside your JavaScript code you can put comments. These are ignored by the JavaScript engine and don't have any effect on how the program works. But they can be invaluable when you revisit your code after a few months, or transfer the code to someone else for maintenance.

Two types of comments are allowed:

Some examples:

// beginning of line
var a = 1; // anywhere on the line
/* multi-line comment on a single line */	
/* 
    comment
    that spans
    several lines
 */

There are even utilities, such as JSDoc, that can parse your code and extract meaningful documentation based on your comments.