Exploring the world of Typescript and the significance of index

I have been struggling with a question on how to correctly use index in TS for some time now. For example...

setup.battle.enemies.forEach(enemy => {
        const _thisMove = enemy.movements.random();

        enemy.curMovement = {
            name    : _thisMove.name,
            damage  : _thisMove.elemental.damage(),
            element : _thisMove.elemental.element,
            setMove() {
                const _resistances = variables().player.resistances;

                let _enemyDamage = Math.round(this.damage - _resistances[this.element]);
            }
        }
    })

In this scenario, _resistances[this.element] is causing an error: Element implicitly has an 'any' type because expression of type 'any' can't be used to index type '{ physical: number; fire: number; ice: number; energy: number; water: number; light: number; darkness: number; }'.ts(7053)

The resistances object in the enemies class is defined as...

this.resistances = {
        physical : 2,
        fire : 0,
        ice : 0,
        energy : 0,
        water : 0,
        light : -2,
        darkness : 0
 };

So my question is, how can I resolve this issue and make it work properly?

The element property is part of the enemies skills array.

this.movements = [
         {
                  name      : "Knife attack",
                  elemental : {
                        element : "physical",
                        damage : () => random(2, 4),
                        getElem : function() { return this.element }
                  }
         }
  ]

Answer №1

If you want to utilize an index for the property resistances, you must first create an interface specifying the structure and then initialize the resistances object based on that interface:

interface Resistances {
  physical: number,
  fire: number,
  ice: number,
  energy: number,
  water: number,
  light: number,
  darkness: number,
  [index: string]: number;
}
const resistances: Resistances = {
  physical: 2,
  fire: 0,
  ice: 0,
  energy: 0,
  water: 0,
  light: -2,
  darkness: 0
}

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