Javascript compare 3 values

Question

I have 3 values that I want to compare f, g and h. I have some code to check that they all equal each other and that none of them are null. I\'ve had a look online but could

Answer 1

Create an array of string and check the existance of next value in there

compareAnswers(a1: string, a2: string, a3: string): boolean {
   this.compareAnswerArr.push(a1);
if (this.compareAnswerArr.includes(a2) == false) {
  this.compareAnswerArr.push(a2);
  if (this.compareAnswerArr.includes(a3) == false) {
    return true;
  } else return false;
}
else return false;}