Dynamically accessing object property in typescript

April 6, 2023

I am making a game in typescript. The game has an inventory system with several values like this:

export const Inventory = {
    food: 0,
    medicine: 0,
    rifleAmmo: 0,
    pistolAmmo: 0
}

Currently I am managing adding and subtracting from the Inventory with the following function

export const removeFromInventory = ({amount}: itemInterface) => {
    return Inventory.rifleAmmo  = Inventory.rifleAmmo - amount 
}

I want to make this function accept a dynamic value for the name and the amount, currently I have this from other answers here on stackoverflow

enum itemType {
    'rifle-ammo'
}
interface itemInterface {
    amount: number,
    item: itemType
}
export const AddToInventory = ({amount, item}: itemInterface) => {
    return  Inventory[item]  = Inventory.item + amount 
}

However I am getting the error that either a string cannot be used as an index type, having the type be "any" doesn’t help either. I know this is possible but my typescript skills are lacking.
How can I dynamically access an object’s property in typescript?

>Solution :

You could do it like this

type inventory = typeof Inventory;
export const Inventory = {
    food: 0,
    medicine: 0,
    rifleAmmo: 0,
    pistolAmmo: 0
}

enum itemType {
    'rifle-ammo'
}
interface itemInterface {
    amount: number,
    item: keyof inventory
}
export const AddToInventory = ({amount, item}: itemInterface) => {
    return  Inventory[item]  = Inventory[item] + amount 
}