Kieran Barker

Declare multiple JavaScript variables in one statement

You can declare JavaScript variables one at a time like so: var myName = "Kieran";. But did you know you can declare more than one at a time using a single var statment?

Let’s say I wanted to declare my name and my dog’s name at the same time. Instead of doing this:

var myName = "Kieran";
var dogName = "Yoko";

I could just do this:

var myName = "Kieran", dogName = "Yoko";

The only trouble is, it can cause some confusion.

It’s possible to declare variables without initializing them; for example, I could declare var myName;. That would create the variable without assigning it a value, so it would just be undefined. I could then assign a value to it later on in the script.

That’s fine, but when I’ve taken it a step further and written things like the following, it’s confused other developers:

var myName, dogName = "Yoko";

This is because, in my opinion, it looks like I’m assigning the same value to both myName and dogName. In reality, I’m declaring myName without assigning it a value (so it’s undefined) while assigning the string Yoko to dogName.

Just something to be aware of in case you see it in the wild!