Question

Is this allowed?

myObj = {};
myObj['4a56546s6d']

Or the key must start with a letter like:

myObj = {};
myObj['x4a56546s6d']

Can I mix both like:

myObj = {};
myObj['x4a56546s6d']
myObj['4a56546s6d']

I ask that because somethings (for example an ID in HTML) must begin with a letter. I have at the moment the third version and the fireBug marks the keys (beginning with a number) blue.

Answer 1

You can use any key if you use [string] to access the key, even key with space. All of these are valid:

myObj['key with space']
myObj['12345']

But if you want to use dot . operator to access the key then the key must be a valid identifier which means they can not begin with a number or contain space.