How to create an array in JavaScript whose indexing starts at 1?

It isn't trivial. It's impossible. The best you could do is create an object using numeric properties starting at 1 but that's not the same thing.

Why exactly do you want it to start at 1? Either:

• Start at 0 and adjust your indices as necessary; or

• Start at 0 and just ignore index 0 (ie only use indices 1 and up).

A simple solution is to fill the zeroth item:

var map = [null, 'January', 'February', 'March'];
'First month : ' + map[1];

Semantically it would be better to use an object:

var map = {1:'January', 2:'February', 3:'March'};
'First month : ' + map[1];

Note these keys are not ints actually, object keys are always strings.
Also, we can't use dot notation for accessing. (MDN - Property Accessors)

I'd choose the first solution, which I think is less confusing.

Since this question also pops up for a Google search like "javascript start array at 1" I will give a different answer:

Arrays can be sliced. So you can get a sliced version of the Array like this:

var someArray = [0, 1, 2, 3];

someArray.slice(1);
[1, 2, 3]

someArray.slice(2, 4);
[2, 3]

Source: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/slice