TypeScript Generic Collection: List - list

Question

I am trying to learn TypeScript, and need some advice on implementing generic collection types. I put the dictionary and HashSet in another question, here I'd like any advice on my list type.
Especially the ForEach-Operation looks a bit strange. I think I found it in another question here, and "improved" by returning true or false to give feedback if the iteration was stopped early or completed.
import { IForEachFunction } from "./IForEachFunction"
export class List<T> {
private _items: Array<T>;
public constructor() {
this._items = [];
}
public get Count(): number {
return this._items.length;
}
public Item(index: number): T {
return this._items[index];
}
public Add(value: T): void {
this._items.push(value);
}
public RemoveAt(index: number): void {
this._items.splice(index, 1);
}
public Remove(value: T): void {
let index = this._items.indexOf(value);
this.RemoveAt(index);
}
public ForEach(callback: IForEachFunction<T>): boolean {
for (const element of this._items) {
if (callback(element) === false) {
return false;
}
}
return true;
}
}
The ForEach-Iteration relies on an interface from another file:
export interface IForEachFunction<T> {
(callback: T): boolean | void;
}
You would use my list and the ForEach-Method like this:
let myList: List<a_type> = new List<a_type>();
let completed: boolean = myList.ForEach(xyz => {
// do something with xyz
return false; // aborts the iteration
return true; // continues with the next element
});
if (completed) // we can see what happened "during" the iteration
I think this is not bad, but I'd appreciate any input. I am not sure if I use the === correctly.
Another question which I really like to know: How could I define a function with the interface IForEachFunction? I do not really "re-use" that interface visibly, I always declare an anonymous method as shown above. If I wanted to call a method having the interface definition, is that possible?
Thanks!
Ralf

Answer 1

One problem I see is that you have an interface instance:
callback: IForEachFunction<T>
This contains a method called
callback()
But you only call callback once. You would have call callback() method inside your interface:
callback.callback()
Also your code looks like it is inspired by C# or Java. In TypeScript you would often just use an array. This simplifies certain code constructs.