How to adjust randomization level javascript [closed]

Question

I'm developing 8 puzzle game using javascript, I shuffle the tiles by shuffling the puzzle tiles array

var shuffleArray = (array) => {
  var currentIndex = array.length, temporaryValue, randomIndex;
  while (0 !== currentIndex) {
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }
  return array;
};

I want to give the user the option to choose difficulty: easy, medium, hard, How can I implment this?

Update:

I will explain a little bit my implmentation. (this is typescript)

The puzzle array is an array of class PuzzleNode

export class PuzzleNode {
  goal: Node;
  current: Node;
}

When I shuffle I don't touch the puzzleArray but I shuffle the current property like so

shuffle() {
   this.shuffledNodes = shuffleArray(this.shuffledNodes);
   for (let i = 0; i < this.shuffledNodes.length; i++) {
     this.puzzleNodes[i].current = this.shuffledNodes[i];
   }
   /** Keep shuffling until getting a solvable puzzle */
   if (!this.isSolvable()) {
     this.shuffle();
    }
}

This way I can reach any node using the index, because the index doesn't change even after shuffling, for instance the blank tile is always puzzleNodes[8]

Answer 1

The way to vary the difficulty would be to reduce or increase the number of moves required to solve it.

I think the best way to go about this is to implement the shuffling algorithm as a reverse of the way it will be solved: while shuffling, only pick legal moves (move a piece into an adjacent gap), and repeat this randomly for a certain number of moves until it's sufficiently shuffled.

For easy mode, only do about 5 moves. For hard, do 30 moves. A puzzle that requires 5 moves to solve will be a lot easier.