Class constructor type in typescript

Question

How can I declare a class type  so that I ensure the object is a constructor of a general class    In the following example  I want to know which type should I give to AnimalClass so that it could either be Penguin or Lion   class Animal       constructor             console log  Animal             class Penguin extends Animal       constructor             super            console log  Penguin             class Lion extends Animal       constructor             super            console log  Lion             class Zoo       AnimalClass  class    AnimalClass could be  Lion  or  Penguin       constructor AnimalClass  class            this AnimalClass   AnimalClass         let Hector   new AnimalClass              Of course  the class type does not work  and it would be too general anyway

User · Answer

How can I declare a class type  so that I ensure the object is a constructor of a general class    A Constructor type could be defined as    type AConstructorTypeOf lt T gt    new     args any      gt  T    class A           function factory Ctor  AConstructorTypeOf lt A gt       return new Ctor        const aInstance   factory A

User · Answer

Solution from typescript interfaces reference   interface ClockConstructor       new  hour  number  minute  number   ClockInterface    interface ClockInterface       tick       function createClock ctor  ClockConstructor  hour  number  minute  number   ClockInterface       return new ctor hour  minute      class DigitalClock implements ClockInterface       constructor h  number  m  number          tick             console log  beep beep            class AnalogClock implements ClockInterface       constructor h  number  m  number          tick             console log  tick tock             let digital   createClock DigitalClock  12  17   let analog   createClock AnalogClock  7  32     So the previous example becomes   interface AnimalConstructor       new     Animal     class Animal       constructor             console log  Animal             class Penguin extends Animal       constructor             super            console log  Penguin             class Lion extends Animal       constructor             super            console log  Lion             class Zoo       AnimalClass  AnimalConstructor    AnimalClass can be  Lion  or  Penguin       constructor AnimalClass  AnimalConstructor            this AnimalClass   AnimalClass         let Hector   new AnimalClass

User · Answer

Like that   class Zoo       AnimalClass  typeof Animal       constructor AnimalClass  typeof Animal             this AnimalClass   AnimalClass         let Hector   new AnimalClass              Or just   class Zoo       constructor public AnimalClass  typeof Animal             let Hector   new AnimalClass              typeof Class is the type of the class constructor  It s preferable to the custom constructor type declaration because it processes static class members properly   Here s the relevant part of TypeScript docs  Search for the typeof  As a part of a TypeScript type annotation  it means  give me the type of the symbol called Animal  which is the type of the class constructor function in our case

User · Answer

I am not sure if this was possible in TypeScript when the question was originally asked  but my preferred solution is with generics   class Zoo lt T extends Animal gt        constructor public readonly AnimalClass  new      gt  T              This way variables penguin and lion infer concrete type Penguin or Lion even in the TypeScript intellisense   const penguinZoo   new Zoo Penguin   const penguin   new penguinZoo AnimalClass        penguin  is of  Penguin  type   const lionZoo   new Zoo Lion   const lion   new lionZoo AnimalClass        lion  is  Lion  type

[class] Class constructor type in typescript?

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