what is new() in Typescript?

Question

I encountered new() in the official document here about generics.

Here is the code context:

function create(c: { new(): T; } )         


        

Answer 1

So in the documentation is mentions that the syntax is for "When creating factories in TypeScript using generics".

If you look at a larger example that they have:

class BeeKeeper {
    hasMask: boolean;
}

class ZooKeeper {
    nametag: string;
}

class Animal {
    numLegs: number;
}

class Bee extends Animal {
    keeper: BeeKeeper;
}

class Lion extends Animal {
    keeper: ZooKeeper;
}

function findKeeper (a: {new(): A;
    prototype: {keeper: K}}): K {

    return a.prototype.keeper;
}

findKeeper(Lion).nametag;  // typechecks!

a: {new(): A
// is actually creating a new instance of the type A which is extending Animal.
// it is necessary to refer to class types by their constructor functions