Something like this should work (I used NodeJs console):

> let a = ['a','a','a','b','b','a','b']
undefined
> a
[
  'a', 'a', 'a',
  'b', 'b', 'a',
  'b'
]
> var result = []
> for (var i = 0; i < a.length; i++){
... result.push(a[i].charCodeAt(0))
... }
7
> result
[
  97, 97, 97, 98,
  98, 97, 98
]

You can do it like so.

You can only get the char code of an index in a string. Since we have an char array we can alsways get the index of 0. The smallest charcode is of A which is 65. In this example I transform a to A which resolves to 65 then I remove 64 since a should be 1. Consecutively b is mapped to B which is 65 and resolves to 2 since 64 is removed

const arr = ['a','a','a','b','b','a','b']


const res = arr.map(char => char.toUpperCase().charCodeAt(0) - 64)
console.log(res)

let a =1;
let b =2;
let  arr = [a,a,a,b,b,a,b]

arr = arr.map((x) => {
    return x.toString()
})

console.log(arr)