the deep meaning of ArrayBufferLike's typescript definition

Question

What\'s the meaning of the typescript definition for ArrayBufferLike?

interface ArrayBufferTypes {
    ArrayBuffer: ArrayBuffer;
}
type ArrayBu         


        

Answer 1

The reason is to allow ArrayBufferTypes to be extended using declaration merging.

This single-member interface is defined in lib.es5.d.ts

interface ArrayBufferTypes {
    ArrayBuffer: ArrayBuffer;
}

But the interface with the same name, but having another member, is defined in es2017.sharedmemory.d.ts

interface ArrayBufferTypes {
    SharedArrayBuffer: SharedArrayBuffer;
}

When both type declarations are included in the program, declarations will be merged and the resulting union type

type ArrayBufferLike = ArrayBufferTypes[keyof ArrayBufferTypes];

will have two members now: ArrayBuffer and SharedArrayBuffer.