Generating the alphabet in JavaScript
Alternative to String.fromCharCode
... if you are happy with a lowercase only alphabet.

for(i=9,a='';++i&lt;36;)a+=i.toString(36) // 38, cannot be used in an expression
[...Array(26)].map(_=&gt;(++i).toString(36),i=9).join`` // 52 directly returnig the string desired
[...Array(26)].map(_=&gt;a+=(++i).toString(36),a='',i=9) // 53 assign to a variable
(i=9,[for(_ of Array(26))(++i).toString(36)].join``) // 52 ES7 direct return
i=9,a='',[for(_ of Array(26))a+=(++i).toString(36)] // 51 ES7 assign to a variable