Complementary DNA.js

// Deoxyribonucleic acid (DNA) is a chemical found in the nucleus of cells and carries the "instructions" for the development and functioning of living organisms.

// If you want to know more http://en.wikipedia.org/wiki/DNA

// In DNA strings, symbols "A" and "T" are complements of each other, as "C" and "G". You have function with one side of the DNA (string, except for Haskell); you need to get the other complementary side. DNA strand is never empty or there is no DNA at all (again, except for Haskell).

// More similar exercise are found here http://rosalind.info/problems/list-view/ (source)

// DNAStrand ("ATTGC") // return "TAACG"

// DNAStrand ("GTAT") // return "CATA"

function DNAStrand(dna) {
  return dna.replace(/[A-Z]/g, (l) =>
    l === 'A' ? 'T' : l === 'T' ? 'A' : l === 'C' ? 'G' : 'C'
  )
}

console.log(DNAStrand('AAAA'), 'TTTT', 'String AAAA is')
console.log(DNAStrand('ATTGC'), 'TAACG', 'String ATTGC is')
console.log(DNAStrand('GTAT'), 'CATA', 'String GTAT is')