Suggestion: a built-in TypedArray interface

I would have expected a TypedArray interface to exist in the built-in declaration libraries. Instead, there are independent types for Int8Array, etc, with no common base type.

interface Int8Array { /* ... */ }
interface Int8ArrayConstructor { /* ... */ }
declare const Int8Array: Int8ArrayConstructor;

interface Uint8Array { /* ... */ }
interface Uint8ArrayConstructor { /* ... */ }
declare const Uint8Array: Uint8ArrayConstructor;

// ...

It seems sensible that there should be a common TypedArray type, both because

• a TypeScript user might want to declare a variable as a TypedArray, and
• it would reduce repetition in the built-in declaration files

interface TypedArray { /* ... */ }

interface Int8Array extends TypedArray { }
interface Int8ArrayConstructor { /* ... */ }
declare const Int8Array: Int8ArrayConstructor;

interface Uint8Array extends TypedArray { }
interface Uint8ArrayConstructor { /* ... */ }
declare const Uint8Array: Uint8ArrayConstructor;

// ...

Is there a good reason why there is no TypedArray type? If not, I can submit a PR.

Use case

Consider the isTypedArray() function from lodash. Currently, it is declared as follows:

function isTypedArray(value: any): boolean;

This proposal would enable an appropriate type-guard, without declaring a convoluted union type:

function isTypedArray(value: any): value is TypedArray;

[mhegazy]

You can achieve the same behavior today by defining:

type TypedArray = Int8Array | Uint8Array | Int16Array | Uint16Array | Int32Array | Uint32Array | Uint8ClampedArray | Float32Array | Float64Array;

but in general define one TypedArray interface and use this types should reduce the duplication.

[patrickroberts]

@dschnelldavis new doesn’t work because it’s essentially an abstract constructor, for lack of a better terminology. However, instanceof does work as demonstrated in this snippet:

const TypedArray = Object.getPrototypeOf(Uint8Array)
console.log(new Uint8Array() instanceof TypedArray)

As other people have said, even though it’s an invisible constructor, there should still be an interface for it, as it encapsulates a lot of functionality in a single base class and drastically reduces repetition for definition files, as well as more accurately reflecting the specification.

I think there should also be an interface for TypedArrayConstructor as well, since there are common static properties, so something like this:

interface TypedArray {
  ...
}

interface TypedArrayConstructor {
  readonly prototype: TypedArray;
  ...
}

interface Float32Array extends TypedArray { }
interface Float64Array extends TypedArray { }
interface Int16Array extends TypedArray { }
interface Int32Array extends TypedArray { }
interface Int8Array extends TypedArray { }
interface Uint16Array extends TypedArray { }
interface Uint32Array extends TypedArray { }
interface Uint8Array extends TypedArray { }
interface Uint8ClampedArray extends TypedArray { }

interface Float32ArrayConstructor extends TypedArrayConstructor { }
interface Float64ArrayConstructor extends TypedArrayConstructor { }
interface Int16ArrayConstructor extends TypedArrayConstructor { }
interface Int32ArrayConstructor extends TypedArrayConstructor { }
interface Int8ArrayConstructor extends TypedArrayConstructor { }
interface Uint16ArrayConstructor extends TypedArrayConstructor { }
interface Uint32ArrayConstructor extends TypedArrayConstructor { }
interface Uint8ArrayConstructor extends TypedArrayConstructor { }
interface Uint8ClampedArrayConstructor extends TypedArrayConstructor { }