constructor(initialCapacity = 19, loadFactor = 0.75) {
    this.initialCapacity = initialCapacity;
    this.loadFactor = loadFactor;
    // end::constructorPartial[]
    this.reset();
  }
Initialize array that holds the values.
@param {number} initialCapacity initial size of the array (preferably a prime)
@param {number} loadFactor rehash is called when this threshold is met.