how would you assign numbers to letters in js code example

Example: javascript letters as number

const toChars = n => `${n >= 26 ? toChars(Math.floor(n / 26) - 1) : ''}${'ABCDEFGHIJKLMNOPQRSTUVWXYZ'[n % 26]}`;

// Examples
toChars(0);     // A
toChars(1);     // B
toChars(25);    // Z