Having difficulty specifying the class type in Typescript

I am currently working on defining a 'Definition' type in Typescript. In this case, a Definition could be either a class constructor or an object. Here is the code snippet that illustrates my approach:

 if (this._isConstructor(definition)) {
  return new definition(...args); // if it is a class, instantiate it
 }

return definition; // if it is an object, just return it

The initial way I defined my type was as follows:

type Definition = {
  new (arg?: object): object | object
}

This method works but appears somewhat messy. As a result, I decided to split it into separate types:

type Definition = {
 Cstruct | object
}

type Cstruct = new (arg?: object): object

However, this modification resulted in an error message stating:

Cannot use 'new' with an expression whose type lacks a call or construct signature

whenever attempting to utilize the 'new' keyword.

Answer №1

An example of utilizing a type guard in action:

type Item = Product | object
type Product = {new (params?: object): object}

function isProduct(item: Item): item is Product {
  // Implement your logic here to determine if it's a product or not
  return true 
}

function getItem(item: Item, params = []) {
  if (isProduct(item))
    return new item(...params);
  return item;
}

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