Nowadays JavaScript has three different keywords to declare a variable — var, let and, const. Each has its own properties and particularities. Let’s start by making a simple comparison table ...

JavaScript variable names can be almost unlimited in length, although for practical reasons you’ll probably want to keep your variable names under 10 or 15 characters.

Ah, I see! You're using names, not IDs. The possibility didn't occur to me immediately because names on form elements are deprecated in XHTML 1.0, and that's usually all I use.