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". Your function receives one side of the DNA (string, except for Haskell); you need to return 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)

// Example: (input --> output)

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

//P: string
//R: return the other complementary side A -> T, T->A, G ->G and C->G
//E:
//P:

function DNAStrand(dna){

    output =''
    for(let item of dna){
      if(item == 'A')
        output += 'T'
      else if(item == 'T')
         output += 'A'
      else if(item == 'G')
        output += 'C'
      else if(item == 'C')
        output += 'G'
    }
    return output
  }
  console.log(DNAStrand("AAAA"),"TTTT","String AAAA is")
  console.log(DNAStrand("ATTGC"),"TAACG","String ATTGC is")
  console.log(DNAStrand("GTAT"),"CATA","String GTAT is") 
  // DNAStrand("AAAA")
  // DNAStrand("GTAT")
  //DNAStrand("aaaa")