Optix

npm install optix

Optix is a data manipulation library that can focus on one or many elements in a nested structure to get or set their values. Optix features robust Typescript support and is smaller and faster than true optics libraries.

• Simple yet powerful: optics-like capabilities with a simple, intuitive syntax
• Type-safe: Robust type checking with minimal type annotations
• Tiny: < 1kb gzipped, zero dependencies

Usage

Let's say we have the following data structure

import { get, set, find, filter, remove, all } from 'optix'

const state1 = {
    title: 'Introduction',
    steps: [
        { title: 'Introduce get', completed: false },
        { title: 'Introduce set', completed: false },
        { title: 'Introduce find', completed: false },
        { title: 'Introduce filter', completed: false },
        { title: 'Introduce remove', completed: false },
        { title: 'Introduce all', completed: false },
    ]
}

We can focus on the title of the first step and get its value

get('steps', 0, 'title')(state1)
// 'Introduce get'

We can focus on the completed key of the first two steps and set them both to true

const state2 = set('steps', [0, 1], 'completed')(true)(state1)
// {
//     title: 'Introduction',
//     steps: [
//         { title: 'Introduce get', completed: true },
//         { title: 'Introduce set', completed: true },
//         { title: 'Introduce find', completed: false },
//         { title: 'Introduce filter', completed: false },
//         { title: 'Introduce remove', completed: false },
//         { title: 'Introduce all', completed: false },
//     ]
// }

We can find the index of a step to focus on and set it to be completed

const state3 = set('steps', find(step => step.title === 'Introduce find'), 'completed')(true)(state2)
// {
//     title: 'Introduction',
//     steps: [
//         { title: 'Introduce get', completed: true },
//         { title: 'Introduce set', completed: true },
//         { title: 'Introduce find', completed: true },
//         { title: 'Introduce filter', completed: false },
//         { title: 'Introduce remove', completed: false },
//         { title: 'Introduce all', completed: false },
//     ]
// }

We can focus on the incomplete steps with a filter and get their titles

get('steps', filter(step => !step.completed), 'title')
// ['Introduce filter', 'Introduce remove', 'Introduce all']

We can focus on all the steps and remove their completed keys

const state4 = remove('steps', all, 'completed')(state3)
// {
//     title: 'Introduction',
//     steps: [
//         { title: 'Introduce get' },
//         { title: 'Introduce set' },
//         { title: 'Introduce find' },
//         { title: 'Introduce filter' },
//         { title: 'Introduce remove' },
//         { title: 'Introduce all' },
//     ]
// }

We can even find and filter items in maps/records

import { get, findByVal, filterByVal } from 'optix'

const state = {
    users: {
        alice: { name: 'Alice', age: 22 },
        bob: { name: 'Bob', age: 33 },
        claire: { name: 'Claire', age: 44 },
    }
}

get('users', findByVal(user => user.name.startsWith('C')))(state)
// { name: 'Claire', age: 44 }

get('users', filterByVal(user => user.age < 40))(state)
// [{ name: 'Alice', age: 22 }, { name: 'Bob', age: 33 }]

API Reference

Main Functions

The main functions all take any number of PathItems to form a Path. Each PathItem can focus on one or many elements in an object or array.

type GetKey = (map: { [key: string]: any }) => string | undefined
type GetKeys = (map: { [key: string]: any }) => string[]
type GetIndex = (arr: any[]) => number | undefined
type GetIndexes = (arr: any[]) => number[]

type PathItem = string | number | string[] | number[] | GetKey | GetIndex | GetKeys | GetIndexes

type Path = PathItem[]

All updates are performed immutably

get

path => object => valueAtPath

get('foo', 'bar')({ foo: { bar: 'baz' } })
// 'baz'

get('letters', [0, 1])({ letters: ['a', 'b', 'c'] })
// ['a', 'b']

get('letters', arr => arr.length - 1)({ letters: ['a', 'b', 'c'] })
// 'c'

set

path => newValueAtPath => object => updatedObject

set('foo', 'bar')('BAZ')({ foo: { bar: 'baz' } })
// { foo: { bar: 'BAZ' } }

set('letters', [0, 1])('z')({ letters: ['a', 'b', 'c'] })
// { letters: ['z', 'z', 'c'] }

set('letters', arr => arr.length - 1)('z')({ letters: ['a', 'b', 'c'] })
// { letters: ['a', 'b', 'z'] }

update

path => updaterAtPath => object => updatedObject

const toUpper = str => str.toUpperCase()

update('foo', 'bar')(toUpper)({ foo: { bar: 'baz' } })
// { foo: { bar: 'BAZ' } }

update('letters', [0, 1])(toUpper)({ letters: ['a', 'b', 'c'] })
// { letters: ['A', 'B', 'c'] }

update('letters', arr => arr.length - 1)(toUpper)({ letters: ['a', 'b', 'c'] })
// { letters: ['a', 'b', 'C'] }

remove

path => object => updatedObject

remove('foo', 'bar')({ foo: { bar: 'baz' } })
// { foo: {} }

remove('letters', [0, 1])({ letters: ['a', 'b', 'c'] })
// { letters: ['c'] }

remove('letters', arr => arr.length - 1)({ letters: ['a', 'b', 'c'] })
// { letters: ['a', 'b'] }

Array query helpers

Optix provides helper functions that can be used within paths to find or filter items in an array

import { get, all, filter, find, last } from 'optix'

const arrayHelpers = [
    { name: 'all', type: 'traversal' },
    { name: 'filter', type: 'prism' },
    { name: 'find', type: 'lens' },
    { name: 'last', type: 'lens' },
]

all - focus on all items in the array

array => index

get(all, 'name')(arrayHelpers)
// ['all', 'filter', 'find', 'last']

filter - focus on all items that match the predicate

predicate => array => indexes

get(filter(helper => helper.type === 'prism'), 'name')(arrayHelpers)
// ['filter']

find - focus on the first item that matches the predicate

predicate => array => index

get(find(helper => helper.type === 'lens'), 'name')(arrayHelpers)
// 'find'

last - focus on the last item in the array

array => index

get(last, 'name')(arrayHelpers)
// 'last'

Record query helpers

Optix provides helper functions that can be used within paths to find or filter items in a record/map

import { get, filterByKey, filterByVal, findByKey, findByVal, keys } from 'optix'

const recordHelpers = {
    filterByKey: { description: 'Filter By Key', type: 'prism', predicate: 'key' },
    filterByVal: { description: 'Filter By Value', type: 'prism', predicate: 'value' },
    findByKey: { description: 'Find By Key', type: 'lens', predicate: 'key' },
    findByVal: { description: 'Find By Value', type: 'lens', predicate: 'value' },
    keys: { description: 'All Keys', type: 'traversal' },
}

filterByKey - focus on all items that match the predicate

predicate => record => keys

get(filterByKey(key => key.startsWith('filterBy')), 'description')(recordHelpers)
// ['Filter By Key', 'Filter By Value']

filterByVal - focus on all items that match the predicate

predicate => record => keys

get(filterByVal(val => val.type === 'prism'), 'description')(recordHelpers)
// ['Filter By Key', 'Filter By Value']

findByKey - focus on the first item that matches the predicate

predicate => record => key

get(findByKey(key => key.startsWith('findBy')), 'description')(recordHelpers)
// 'Find By Key'

findByVal - focus on the first item that matches the predicate

predicate => record => key

get(findByVal(val => val.type === 'lens' && val.predicate === 'value'), 'description')(recordHelpers)
// 'Find By Value'

keys - focus on all items in the object

record => key

get(keys, 'description')(recordHelpers)
// ['Filter By Key', 'Filter By Value', 'Find By Key', 'Find By Value', 'All Keys']

Creating custom query helpers

Custom query helpers are easy to make, they just need to return one or more keys or indexes. Lodash's findIndex and findKey can be used as drop-in replacements for find and findByVal respectively.

Invalid keys

Keys must be strings or non-negative numbers. Operations will halted if an invalid key is found.

// find will return -1 since Dave does not exist in the array
// a shallow copy of the array will be returned, no element will be modified
set(find(person => person.name === 'Dave'), 'name')('David')([{ name: 'Alice' }, { name: 'Bob' }])
// [{ name: 'Alice' }, { name: 'Bob' }]

TypeScript Notes

get does not require any typings

const getFooCompleted = get('foo', 'completed') // expect type { foo: { completed: unknown } }
const bool = getFooCompleted({ foo: { completed: false } }) // return type is boolean
// false

set does not require any typings

if the new value is missing keys the return type will be unknown

const setFooCompleted = set('foo', 'completed')(true) // expect type { foo: { completed: boolean } }
const completedFoo = setFooCompleted({ foo: { completed: false } }) // return type same as final argument type
// { foo: { completed: true } }

update requires the updater to be typed

if the new value is missing keys the return type will be unknown

const obj = { foo: { completed: false } }
const toggleFooCompleted1 = update('foo', 'completed')((bool: boolean) => !bool) // expect type { foo: { completed: boolean } }
const toggleFooCompleted2 = update('foo', 'completed')<boolean>((bool) => !bool) // same as above
const completedFoo = toggleFooCompleted1({ foo: { completed: false } }) // return type same as final argument type
// { foo: { completed: true } }

remove does not require explicit typings

if the path targets a required key the return type will be unknown

const foo: { foo: { completed?: boolean } } = { foo: { completed: false } }

const removeFooCompleted = remove('foo', 'completed') // expect type { foo: { completed: unknown } }
const fooWithoutCompleted = removeFooCompleted(foo) // return type same as final argument type
// { foo: {} }

Polymorphism

Optix provides aliased versions of the main functions with typings that support polymorphism

import { polySet, polyUpdate, polyRemove } from 'optix'

// changing boolean to string
polySet('foo')('bar')({ foo: true }) // return type { foo: string }
// { foo: 'bar' }

// removing required key
polyRemove('foo')({ foo: true, bar: true, baz: true }) // return type { bar: boolean; baz: boolean }
// { bar: true, baz: true }

Query Helpers

The find* and filter* helpers can be typed with either a type argument or by typing the callback

interface User {
    name: string
    id: string
}

interface State {
    list: User[]
    map: { [id: string]: User }
}

const state: State = {
    list: [{ name: 'Alice', id: 'A123' }, { name: 'Bob', id: 'B234' }, { name: 'Claire', id: 'C345' }],
    map: {
        A123: { name: 'Alice', id: 'A123' },
        B234: { name: 'Bob', id: 'B234' },
        C345: { name: 'Claire', id: 'C345' }
    }
}

get('list', find<typeof State.list>((user) => user.name === 'Alice'))(state)
get('list', find((user: User) => user.name === 'Alice'))(state)

get('map', findByVal<typeof State.map>((user) => user.name === 'Alice'))(state)
get('map', findByVal((user: User) => user.name === 'Alice'))(state)

Alternate data-first syntax

If you want a data-first, lodash-like syntax there's a set of functions just for you!

these functions do not have full TypeScript support

import { _get, _set, _update, _delete } from 'optix'

_get({ foo: { bar: 'baz' } }, ['foo', 'bar'])
// 'baz'

_set({ foo: { bar: 'baz' } }, ['foo', 'bar'], 'BAZ')
// { foo: { bar: 'BAZ' } }