elm-ts

A porting of The Elm Architecture to TypeScript featuring fp-ts, RxJS and React.

Installation

npm i elm-ts fp-ts rxjs react

Note: fp-ts, rxjs and react are peer dependencies

Differences from Elm

• no ports
• React instead of virtual-dom (pluggable)
• Navigation is based on history

React

import * as React from 'elm-ts/lib/React'
import { render } from 'react-dom'
import * as component from './examples/Counter'

const main = React.program(component.init, component.update, component.view)

React.run(main, dom => render(dom, document.getElementById('app')!))

How to derive decoders from io-ts codecs

import * as t from 'io-ts'
import { failure } from 'io-ts/lib/PathReporter'

function fromCodec<A>(codec: t.Decoder<unknown, A>): Decoder<A> {
  return flow(
    codec.decode,
    E.mapLeft(errors => failure(errors).join('\n'))
  )
}

Enable debugger in development mode

For Html (and its specializations) programs:

import { programWithDebugger } from 'elm-ts/lib/Debug/Html'
import * as React from 'elm-ts/lib/React'
import { render } from 'react-dom'
import * as component from './examples/Counter'

const program = process.env.NODE_ENV === 'production' ? React.program : programWithDebugger

const main = program(component.init, component.update, component.view)

React.run(main, dom => render(dom, document.getElementById('app')!))

For Navigation (and its specializations) programs:

import { programWithDebuggerWithFlags } from 'elm-ts/lib/Debug/Navigation'
import * as Navigation from 'elm-ts/lib/Navigation'
import * as React from 'elm-ts/lib/React'
import { render } from 'react-dom'
import * as component from './examples/Navigation'

const program = process.env.NODE_ENV === 'production' ? Navigation.programWithFlags : programWithDebuggerWithFlags

const main = program(component.locationToMsg, component.init, component.update, component.view)

React.run(main(component.flags), dom => render(dom, document.getElementById('app')!))

Stop the application

If you need to stop the application for any reason, you can use the withStop combinator:

import { withStop } from 'elm-ts/lib/Html'
import * as React from 'elm-ts/lib/React'
import { render } from 'react-dom'
import { fromEvent } from 'rxjs'
import * as component from './examples/Counter'

const stopSignal$ = fromEvent(document.getElementById('stop-btn'), 'click')

const program = React.program(component.init, component.update, component.view)

const main = withStop(stopSignal$)(program)

React.run(main, dom => render(dom, document.getElementById('app')!))

The combinator takes a Program and stops consuming it when the provided Observable emits a value.

In case you want to enable the debugger, you have to use some specific functions from the Debug sub-module:

// instead of `programWithDebuggerWithFlags`
import { programWithDebuggerWithFlagsWithStop } from 'elm-ts/lib/Debug/Navigation'
import { withStop } from 'elm-ts/lib/Html'
import * as Navigation from 'elm-ts/lib/Navigation'
import * as React from 'elm-ts/lib/React'
import { render } from 'react-dom'
import * as component from './examples/Navigation'

const stopSignal$ = fromEvent(document.getElementById('stop-btn'), 'click')

const program =
  process.env.NODE_ENV === 'production'
    ? Navigation.programWithFlags
    : programWithDebuggerWithFlagsWithStop(stopSignal$)

const main = withStop(stopSignal$)(program(component.locationToMsg, component.init, component.update, component.view))

React.run(main(component.flags), dom => render(dom, document.getElementById('app')!))

Examples

• Counter
• Labeled Checkboxes (with a sprinkle of functional optics)
• Task, Time and Option
• Http and Either
• Navigation
• Compose Modules

Documentation

• API Reference