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https://github.com/iagobelo/ts-loupe
Composable getters and setters.
https://github.com/iagobelo/ts-loupe
functional-programming lens typescript
Last synced: about 4 hours ago
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Composable getters and setters.
- Host: GitHub
- URL: https://github.com/iagobelo/ts-loupe
- Owner: iagobelo
- License: mit
- Created: 2020-07-21T16:38:32.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2023-01-07T22:51:50.000Z (about 2 years ago)
- Last Synced: 2024-04-24T15:23:46.024Z (9 months ago)
- Topics: functional-programming, lens, typescript
- Language: TypeScript
- Homepage:
- Size: 1.35 MB
- Stars: 12
- Watchers: 2
- Forks: 0
- Open Issues: 9
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# TS Loupe
[](https://travis-ci.org/iagobelo/ts-loupe)
[](./LICENSE)
[](https://bundlephobia.com/result?p=ts-loupe)
[](https://bundlephobia.com/result?p=ts-loupe)
## About
Lenses is a pattern used to read and update properties within an object.
## Installation
This library is published in the NPM registry and can be installed using any compatible package manager.
```sh
npm install ts-loupe --save
# For Yarn, use the command below.
yarn add ts-loupe
```
### Installation from CDN
This module has an UMD bundle available through JSDelivr and Unpkg CDNs.
```html
```
## API
- [Lens](#lens)
- [View](#view)
- [Set](#set)
- [Over](#over)
- [Prop](#prop)
- [Compose](#compose)
### Lens
Is a pair of two functions that abstracts the way of we access the requested field. In other words is a focus into some data structure.
Signature:
```typescript
type Getter = (data: A) => B;
type Setter = (value: B) => (data: A) => A;
interface Lens {
get: Getter;
set: Setter;
}
```
Example:
```typescript
type User = { name: string; age: number };
const user: User = { name: 'Jerry Lee', age: 18 };
const getName = (user: User) => user.name;
const setName = (name: User['name']) => (data: User) => ({ ...data, name });
const nameLens = lens(getName, setName);
nameLens.get(user); // returns: "Jerry Lee".
nameLens.set('Leon Lan')(user); // returns: A new user with Leon Lan as the name.
```
### View
Returns the data structure pointed to by the lens getter function.
Signature:
```typescript
type LensView = (lens: Pick, 'get'>) => (data: O) => V;
```
Example:
```typescript
type User = { name: string };
const user: User = { name: 'Len Lon' };
const getName = (user: User) => user.name;
const setName = (name: User['name']) => (data: User) => ({ ...data, name });
const nameLens = lens(getName, setName);
view(nameLens)(user); //returns: "Len Lon".
```
### Set
Set is used to 'set' a value into the data structure pointed to by the lens setter function.
Signature:
```typescript
type LensSet = (
lens: Pick, 'set'>
) => (value: V) => (data: O) => O;
```
Example:
```typescript
type User = { name: string };
const user: User = { name: 'Jackie Chan' };
const getName = (user: User) => user.name;
const setName = (name: User['name']) => (data: User) => ({ ...data, name });
const nameLens = lens(getName, setName);
lensSet(nameLens)('John Wick')(user); // returns: A new user with "John Wick" as the name.
```
### Over
Applies the function to the given lens property and returns the result.
Signature:
```typescript
type LensOver = (
lens: Lens
) => (fn: (value: V) => V) => (data: O) => O;
```
Example:
```typescript
type User = { name: string };
const user: User = { name: 'Santino' };
const nameLens = prop('name');
over(nameLens)(name => `${name} D'Antonio`)(user); // returns: A new user with "Santino D'Antonio" as the name.
```
### Prop
Creates a lens focused on a given property.
Signature:
```typescript
type LensProp = (key: K) => Lens;
```
Example:
```typescript
type User = { age: string; name: string };
lensProp('age'); // returns: A lens instance focused on the age propertie.
```
### Compose
Compose two lenses `Lens` and `Lens`, to produce a new lens `Lens`.
Signature:
```typescript
interface LensCompose {
(...lenses: [Lens, Lens]): Lens;
}
```
Example:
```typescript
type User = {
pocket: {
money: number;
};
};
const user: User = {
pocket: {
money: 3213
}
};
const pocketLens = lensProp('pocket');
const moneyLens = lensProp('money');
compose(
pocketLens,
moneyLens
); // returns: A new lens focused on money propertie.
```
## License
Released under [MIT License](./LICENSE).