DNA to RNA

dna2rna.js

// @ts-check
/* eslint no-restricted-syntax: ["off", "ForOfStatement"] */

// BEGIN (write your solution here)
const map = {
  G: "C",
  C: "G",
  T: "A",
  A: "U",
}

export default (dna) =>  {
  const dnaNucleotids = dna.split('')
  let result = ''
  for (const dnaNucleotid of dnaNucleotids) {
    const rnaNucleotid = map[dnaNucleotid]
    if(!rnaNucleotid) {
      result = null
      break
    } else {
      result += rnaNucleotid
    }
  }
  return result
}

// OR 

export default (dna) => {
  const dnaNucleotids = dna.split('')
  const known = (dnaNucleotid) => Object.hasOwn(map, dnaNucleotid)
  const dnaToRnaMapper = (dnaNucleotid) => map[dnaNucleotid]
  return dnaNucleotids.every(known) ? dnaNucleotids.map(dnaToRnaMapper).join('') : null
}

// END