TypeScript类通用参数约束

Question

I'm attempting to declare a TypeScript class with a constrained generic parameter. In C#, the following would compile:

public class NewClass<T> where T: BaseClass {
}

What is the TypeScript equivalent?

Answer 1

You're looking for the extends keyword. You can use it right after the generic parameter to constrain it to be a subtype of the specified type.

So the equivalent for your example would be:

class NewClass<T extends BaseClass> {
    // Things...
}

You can read more about generic constraints in the documentation here .

Answer 2

For both classes and interfaces as base, you have to constrain T like this:

export class NewClass<T extends BaseClass> {
}

While you derive classes from interfaces with implements , the same is not true for generic constraints, making this code possible:

export class NewClass<T extends BaseInterface> implements BaseInterface {
}