Mystery Organism

I am currently working on the [Mystery Organism] (https://www.codecademy.com/practice/projects/mysterious-organism) project and it wants us to compare elements from two separate arrays and count how many elements match.

In my code below, I cannot get the count variable to increment when two elements of the array match. Any idea what the issue could be?

// 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 = (num, bases) => {
  return {
    specimenNum: num,
    dna: bases,
   mutate() {
    const dnaBases = ['A', 'T', 'C', 'G']
    let base = this.dna[Math.floor(Math.random() * this.dna.length)]
    
    let baseNum = this.dna.indexOf(base)
 

    if (base === 'A'){
      dnaBases.splice(0,1);
      this.dna[baseNum] = dnaBases[Math.floor(Math.random() * 3)];
    } else if (base === 'T'){
      dnaBases.splice(1,1);
      this.dna[baseNum] = dnaBases[Math.floor(Math.random() * 3)];
    } else if (base === 'C'){
      dnaBases.splice(2,1);
      this.dna[baseNum] = dnaBases[Math.floor(Math.random() * 3)]
    } else {
       dnaBases.splice(3,1);
      this.dna[baseNum] = dnaBases[Math.floor(Math.random() * 3)]
    };
    return this.dna
},
    
    compareDna(obj) {
      let count = 0
      for (let i = 0; i < this.dna.length; i++) {
          if (this.dna[i] === obj[i]) {
            count++;
          }
      }
      console.log(count);
       console.log(`Specimen #1 and Specimen #2 have ${count / this.dna.length}% DNA in common`);
    },
  }
}
const organism = pAequorFactory(1, mockUpStrand());
const organism2 = pAequorFactory(2, mockUpStrand());
console.log(organism)

console.log(organism2);
//console.log(organism.mutate());
console.log(organism.compareDna(organism2));

Why not try some console.log statements inside your compareDna method? Maybe log the two variables being compared in the if statement and get a better look at what is happening.