Javascript: Unshift to second position of the array

I understand this diagram:

But now my question is... How can I add an element just in the second position of the Array?

If I have this array: (A, C, G, T) and I want to add B...

The result that I want should be: (A, B, C, G, T)

Any suggestions?

Thank you!

Answer

What you want is the splice function:

arr.splice(index, 0, item); will insert item into arr at the specified index.