Complementary-DNA.js

/* 
Example: (input --> output)

"ATTGC" --> "TAACG"
"GTAT" --> "CATA"
*/

const pairs = {'A':'T','T':'A','C':'G','G':'C'};

function DNAStrand(dna){
  return dna.split('').map(function(v){ return pairs[v] }).join('');
}