Better Object.entries

[PCOffline]

Intro

This type changes the behaviour of Object.entries to return more specific types:

Object.entries({ a: 1, b: 2, c: 3 } as const);
// Before change: [string, 1 | 2 | 3][]
// After change: (["a", 1] | ["b", 2] | ["c", 3])[]

Object.entries({ a: true, b: 'string', c: { field: 1 } } as const);
// Before change: [string, true | "string" | { readonly field: 1; }][]
// After change: (["a", true] | ["b", "string"] | ["c", { readonly field: 1; }])[]

Object.entries([1, 2, 3] as const);
// Before change: [string, 1 | 2 | 3][]
// After change: [number, 2 | 1 | 3][]

Caveats

• In TypeScript 5.0, the function would automatically transform any object or array into a read-only object using the const keyword for more specific results. Therefore, the difference between the results of Object.entries in TypeScript 5 would be even bigger, since the as const part would be omitted.
  In earlier versions, for specific results, the as const assertion needs to be added to inputs.
• The order of the elements in the result of Object.entries cannot be relied on, therefore a union of tuples is returned instead of a deterministic tuple (i.e. (["a", 1"] | ["b", 2])[] and not [["a", 1], ["b", 2]])

[PCOffline]

Todo: update readme

[mattpocock]

Please read the section in the readme that describes why we won't make this change.

[PCOffline]

Alright, didn't see it in the GitHub Readme. Makes sense though

[tyilo]

Please read the section in the readme that describes why we won't make this change.

@mattpocock This seems to be gone from the README. Could you add the note here?

[tyilo]

Found it:

Rules we won't add

Object.keys/Object.entries

A common ask is to provide 'better' typings for Object.keys, so that it returns Array<keyof T> instead of Array<string>. Same for Object.entries. ts-reset won't be including rules to change this.

TypeScript is a structural typing system. One of the effects of this is that TypeScript can't always guarantee that your object types don't contain excess properties:

type Func = () => {
  id: string;
};

const func: Func = () => {
  return {
    id: "123",
    // No error on an excess property!
    name: "Hello!",
  };
};

So, the only reasonable type for Object.keys to return is Array<string>.

[PCOffline]

Bruh this issue was closed 3 months ago how'd you even find it