如何在Typescript中动态扩展泛型类（向其添加属性）作为参数？

Question

How to express the following code in TypeScript?

const enhanceClass = (cls) => {
  cls.prototype.add = (a, b) => a + b;
}
class A {}
enhanceClass(A);
const i = new A()
i.add(1, 2);

Answer 1

TypeScript added support for mixin classes in 2.2. Try this:

type Constructor<T = {}> = new (...args: any[]) => T

function enhanced<T extends Constructor>(Base: T) {
  class WithAdd extends Base {
    add(a: number, b: number) {
      return a + b
    }
  }

  return WithAdd
}

const EnhancedA = enhanced(class A {})

const a = new EnhancedA()
a.add(1, 2)

Though it doesn't do the exact same as in your example, I'd argue that mutating the class prototype being passed in is probably not the best practice anyway.