Fetch ascii code for keys using array in JavaScript?

Looking at your question, I guess, you are looking for either finding ASCII code from character or Key Codes/ Char Codes from keys. Not sure about why you have used the word "array" though.

To find ASCII code from character-

var a = 'a';
alert(a.charCodeAt());

List of ASCII Codes[^]

Following links may help finding key codes/char codes
How to find the key code for a specific key[^]
KeyboardEvent.keyCode[^]

Hope, it helps :)
In case you are looking for something else, please let me know with little better description about your problem.