Achieving intellisense functionality in TypeScript without the use of classes

Just dipped my toes into TypeScript, attempting to convert this basic JavaScript code to TypeScript.

Here is the JavaScript code snippet:

Item = {}

Item.buy = function (id) {}
Item.sell = function (id) {}

I prefer not to use classes and would like to utilize Item as a namespace only.

My goal is to have autocompletion suggestions of 'buy' or 'sell' when typing Item.. I attempted the following:

namespace Item {}
interface Item {}

Item:Item = {}

All of these attempts resulted in errors.

In alignment with Phil's response, here is a revised version closer to what I am aiming for:

interface Item {}
const Item: Item = {};

interface Item {
  buy?: Function
}
Item.buy = function () {
  Item.render()
  return "bought"
}

interface Item {
  sell?: Function
}
Item.sell = function () {
  Item.render()
  return "sold"
}

interface Item {
  render?: Function
}
Item.render = function () {
    return 1
}

Regrettably, this also throws errors.

Answer №1

Describe an interface that includes specific properties and method types

interface BuyAndSell {
  buy: (id: unknown) => void;  // make sure to use more precise data types
  sell: (id: unknown) => void; // instead of using "unknown"
}

Utilize this interface when implementing it

const item: BuyAndSell = {
  buy: function (id) {},
  sell: function (id) {},
};

You can define the functions at any point before creating the BuyAndSell implementation...

const buy: BuyAndSell["buy"] = (id) => {};
const sell: BuyAndSell["sell"] = (id) => {};

// or without explicit typings, for example
// const buy = (id: unknown) => {};

// and later...

*const item: BuyAndSell = { buy, sell };

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