title: Javascript Add Element To Array At Specific Index and Remover "Join" Separator
body: <p>I'm aware this question has been asked many times but I can't find the solution to my specific problem. I'm guessing that I need to refactor my code entirely but could use some guidance.</p>
  <p>I am practicing OOP in Javascript. I would like to join an array and add an &quot;and&quot; conjunction before the last element. That way [1, 2, 3] ==&gt; &quot;1, 2, and 3&quot;.</p>
  <p>I have included my code with comments below. As you will see, the current output I'm getting is &quot;1, 2, and, 3&quot;. How can I get rid of the extra comma? Am I going about this the wrong way?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>class Person {
    constructor(first, last, age, gender, interests) {
      this.name = {
        first: first,
        last: last,
      };
      this.age = age;
      this.gender = gender;
      this.interests = interests;
    }
  
    greeting() {
      console.log(`Hi! I'm ${this.name.first} ${this.name.last}.`)
    }
  
    bio() {
      // store the index of the last element of the array in a variable called index
      let index = this.interests.length - 1;
      // store the conjunction for end of array
      let conjunction = " and"
      // insert the conjunction before last element in array
      this.interests.splice(index, 0, conjunction)
      // join the array into a string separated by commas
      let interestsString = this.interests.join(", ");
      console.log(interestsString);
    }
  }
  
  let person1 = new Person('test', 'test', '29', 'Male', ['skiing', 'cooking', 'gardening']);
  
  console.log(person1.bio());</code></pre>
  </div>
  </div>
  </p>