Preventing duplicate values within an array

Currently, I am working on a rather challenging task that is pushing the limits of my brain. The project involves managing data with a 'position' field, which determines the order they are displayed on the client side. Users can adjust the positions of items, and they are limited to a maximum of 8 positions. However, a problem arises when users try to set an item to a position that is already occupied by another item. Is there a way to iterate through the array, identify conflicting positions, and resolve them?

For example, if there are two items with positions 1 and 2, and a user changes the position of the second item to 1, both items will have the same position. In such cases, the first item should increment its position automatically to avoid conflicts.

I have attempted to use a forEach loop to iterate through the array and handle conflicting positions, but it is not yielding the desired results. Is there a specific algorithm or approach that can effectively address this issue?

this.items.forEach((itemRes) => {
      let itemDash = result;
      if (itemRes.position === result.ordinal) {
        if(itemRes.position !== result) {
          itemRes.ordinal++;
        }
      } else if (itemRes.position === this.items.length && itemRes.ordinal >= 8) {
        itemRes.position--;
      }
    })

The provided code snippet showcases my current attempt to check and adjust the positions of array items accordingly.

Answer №1

Shoutout to this awesome gist by Albertein on GitHub

If I've interpreted your query correctly, you're looking for something similar to what's showcased in the link provided. Here's a TypeScript version tailored to your specific scenario:

array = [1, 2, 3, 4, 5];

move(array, element, delta) {
  let index = array.indexOf(element);
  let newIndex = index + delta;

  //At the beginning or end of the array.
  if (newIndex < 0 || newIndex == array.length) return; 

  let indexes = [index, newIndex].sort(); //Sort the indexes
  //Replace from the lowest index, two elements, swapping their positions
  array.splice(indexes[0], 2, array[indexes[1]], array[indexes[0]]); 
}

moveUp(element) {
  this.move(this.array, element, -1);
}

moveDown(element) {
  this.move(this.array, element, 1);
}

Here's the accompanying HTML snippet:

<div *ngFor="let a of array">
  {{a}} 
  <button (click)="moveUp(a)">Move Up</button>
  <button (click)="moveDown(a)">Move Down</button>
</div>

Check out the live demo on StackBlitz!

You might also find this thread helpful: Moving an element within an array :)

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