How to replace numbers with letters with regular expressions in JavaScript?

Question

I have a string of digits and letters like this:

let cad = "123941A120"

I need to convert that with these substitutions: A = 10, B = 11, C = 12, …, Z = 35. For example, the string above would result in the following, with A replaced by 10: 12394110120.

Another example:

Input:  158A52C3
Output: 1581052123

Answer 1

This will do it without having to map all the letter codes, with the assumption that adjacent letters have adjacent codes...

result = "158A52c3".replaceAll(/[A-Z]/ig, (c) => {
    offset = 10;
    return c.toUpperCase().charCodeAt(0) - "A".charCodeAt(0) + offset;
})
    
console.log(result);

Answer 2

You can do:

const arr = [
  { A: 10 },
  { B: 11 },
  { C: 12 },
  // ...
]

const input = '158A52C3'
const output = arr.reduce((a, c) => {
  const [[k, v]] = Object.entries(c)
  return a.replace(new RegExp(k, 'g'), v)
}, input)

console.log(output)

Answer 3

You can do the following:

const letters = {
'A':10,
'B':11,
'C':12
}
let cad = '123941A120'
for(let L in letters){
cad = can.replace(L,letters[L])
}
console.log(cad)

Answer 4

What you’re trying to do is to convert each digit to base 10. As each digit is from the range 0, 1, …, 8, 9, A, B, …, Y, Z, you’re dealing with a base-36 string. Therefore, parseInt can be used:

const convertBase36DigitsToBase10 = (input) => Array.from(input, (digit) => {
    const convertedDigit = parseInt(digit, 36);
    
    return (isNaN(convertedDigit)
      ? digit
      : String(convertedDigit));
  }).join("");

console.log(convertBase36DigitsToBase10("158A52C3")); // "1581052123"
console.log(convertBase36DigitsToBase10("Hello, world!")); // "1714212124, 3224272113!"

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If you really want to stick to regex, the answer by xdhmoore is a good starting point, although there’s no need for “regex dogmatism”.