PickType and OmitType

[ozum]

Hi,

Could you please add PickType and OmitType types similar to Pick and Omit. It would be helpful. They pick and omit properties based on types of values instead of key names:

I changed names to make it more compatible with utility-types. You can change if you have a more appropriate name in your mind.

Types

// From `Base` pick a set of properties with types of `Condition`
type PickType<Base, Condition> = Pick<Base, { [Key in keyof Base]: Base[Key] extends Condition ? Key : never }[keyof Base]>;

// From `Base` remove a set of properties with types of `Condition`
type OmitType<Base, Condition> = Pick<Base, { [Key in keyof Base]: Base[Key] extends Condition ? never : Key }[keyof Base]>;

Usage

type Props = { name: string; age: number; visible: boolean };

type SomeProps = PickType<Props, string | number>;
// Expect: { name: string; age: number }

type OtherProps = OmitType<Props, string | number>;
// Expect: { visible: boolean }

Types are not developed by me. I saw them on a blog post by Piotr Lewandowski and used in several projects.
Credits: https://medium.com/dailyjs/typescript-create-a-condition-based-subset-types-9d902cea5b8c

Thanks,

[piotrwitek]

I like this types, they are definitely useful.

For the name I would propose:

• PickByValue
• OmitByValue

I choose this name because regular pick is picking by key, and PickByValue is picking by the value, check the example below:

Examples:

type PickByValue<Base, Condition> = Pick<
  Base,
  { [Key in keyof Base]: Base[Key] extends Condition ? Key : never }[keyof Base]
>;

type Props2 = { name: string; 0: boolean };

type SomeProps1 = Pick<Props2, 0>;
// Expect: { 0: boolean }

type SomeProps2 = PickByValue<Props2, boolean>;
// Expect: { 0: boolean }

Accepting PR's.

[piotrwitek]

It's merged but I'm blocking the release for the moment. Mainly because there are few other API proposals and until all of them are sorted out I don't want to make a mistake and introduce some breaking changes in the process.

[ProdigySim]

What happened to these? It looks like they got merged, but then they were removed from index.ts... and are now difficult to import.

[zepatrik]

currently:

import { PickByValue, OmitByValue } from 'utility-types/dist/mapped-types'

[piotrwitek]

I'll have some time during weekend, so hopefully I can finish the proposal for this API and make it public

[IssueHuntBot]

@BoostIO has funded $30.00 to this issue.

---

• Submit pull request via IssueHunt to receive this reward.
• Want to contribute? Chip in to this issue via IssueHunt.
• Checkout the IssueHunt Issue Explorer to see more funded issues.
• Need help from developers? Add your repository on IssueHunt to raise funds.

[IssueHuntBot]

@piotrwitek has rewarded $21.00 to @piotrwitek. See it on IssueHunt

• 💰 Total deposit: $30.00
• 🎉 Repository reward(20%): $6.00
• 🔧 Service fee(10%): $3.00