How To Change the Specimen Number & Not Sure Where the 'undefined' is Coming - Now Solved

Hi again Everyone, I am testing out my code and its partially working but I can’t get the specimen number to change. It’s logging ‘specimen 1 and specimen 1’ to the console. I’ve tried to log (org1.specimenNum.compareDNA(org2.specimenNum) but that brings back a type error. Here’s a link to the project Link .

Also, after logging to the console, it’s returning undefined under the console.log statement. I can’t figure out where that is coming from.

As always, I really appreciate your help!

EDIT: I’ve figured out how to put the specimen number in. For anyone who wants to know its:

console.log('Specimen ' + this.specimenNum + ' and specimen ' + specimen.specimenNum + ' have ' + p + ' percent DNA in common.');

Second EDIT: I just called the compareDNA method instead of logging it the console and it’s no longer returning undefined.

// 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,
      mutate() {
        let dnaM = this.dna[Math.floor(Math.random() * this.dna.length)];
        let randI = [Math.floor(Math.random() * 14)];
        this.dna.splice(randI, 1, dnaM);
        if (this.dna === mockUpStrand) {
          mutate()
        } else {
          this.dna;
        }      
        },
      compareDNA(specimen) {
        let zip = [];
        let array1 = this.dna;
        let array2 = specimen.dna;
        let matchCount = 0
        for (let i = 0; i < array1.length; i++) {
          zip.push([array1[i], array2[i]]);
          if (array1[i] === array2[i]) {
          matchCount++;
        }
        }
        let percent = (matchCount / 15) * 100;
        let p = percent.toFixed();
          console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum + ' have ' + p + ' percent DNA in common.');
          }
        } 
      }


org1 = (pAequorFactory(1, mockUpStrand()));
org2 = (pAequorFactory(2, mockUpStrand()));
console.log(org1.compareDNA(org2));