main.js

// Returns a random DNA base
const returnRandBase = () => {
  const dnaBases = ['A', 'T', 'C', 'G']
  return dnaBases[Math.floor(Math.random() * 4)] 
}

// Returns a random single stand of DNA containing 15 bases
const mockUpStrand = () => {
  const newStrand = []
  for (let i = 0; i < 15; i++) {
    newStrand.push(returnRandBase())
  }
  return newStrand
}

const pAequorFactory = (specimenNum, dna) => {
   return {
      specimenNum : specimenNum,  dna: dna,
      compareDNA (pAequor) {
        let count = 0;
        for(let i = 0 ; i< this.dna.length ; i++) {
           if(this.dna[i]=== pAequor.dna[i]) {
             count++;
           }
        }
        let percentage = Math.round((count/this.dna.length) * 100);
        console.log(`specimen #${this.specimenNum} and specimen #${pAequor.specimenNum} have ${percentage}% DNA in common`);
     },

    mutate() {
    let  baseToMutate = Math.floor(Math.random()* this.dna.length-1);
    let newBase ; 
      do{//mutation base must be different mutated base
           newBase = returnRandBase();
        } while (this.dna[baseToMutate] === newBase)
     this.dna[baseToMutate] = newBase;
    return this.dna;
   },
   willLikelySurvive(){
     let count = 0;
        for(let i = 0 ; i< this.dna.length ; i++) {
           if(this.dna[i]=== 'C' || this.dna[i]==='G') {
             count++;
           }
        }
        let percentage = (count/this.dna.length) * 100;
        return percentage >= 60;
   }

   }
}

const pAequors = [];
let pAeqourWillSurvive;
for(let j=0; j<30;j++) {
   do{
    pAeqourWillSurvive = pAequorFactory(j,mockUpStrand());
   } while(!pAeqourWillSurvive.willLikelySurvive()) 
   pAequors.push(pAeqourWillSurvive);
}


pAequors.forEach( pAequor =>{
  console.log('specimenNum: ' +pAequor.specimenNum);
  console.log('DNA:         ' + pAequor.dna);
  console.log('Likely to Survive: ' +pAequor.willLikelySurvive());
  console.log('Mutated DNA: ' +pAequor.mutate());
  
});

for(let j=1; j< pAequors.length; j++) {
  pAequors[j-1].compareDNA(pAequors[j]);
}