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July 27, 2023 10:32
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Save whiteinge/0c5668ee565df6e9f21aef83f089dd2a to your computer and use it in GitHub Desktop.
Example of a Mealy state machine (initial pattern stolen from somewhere that I forgot to cite)
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| <!doctype html> | |
| <html lang=en> | |
| <head> | |
| <meta charset=utf-8> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| </head> | |
| <body> | |
| <script src="./index.js"></script> | |
| </body> | |
| </html> |
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| var emoji = { | |
| cyclone: String.fromCodePoint(0x1f300), | |
| check: String.fromCodePoint(0x2705), | |
| cross: String.fromCodePoint(0x274c), | |
| } | |
| const ready = (fn, win = window) => { | |
| if (win.readyState !== 'loading') { | |
| fn(); | |
| } else { | |
| win.addEventListener('DOMContentLoaded', fn); | |
| } | |
| } | |
| const spinner = () => `<span class="spinner">${emoji.cyclone}</span>` | |
| const render = state => document.body.innerHTML = ` | |
| <div> | |
| <button | |
| onclick="machine.dispatch('click')" | |
| ${state === 'loading' ? 'disabled' : ''}> | |
| Click ${state === 'loading' ? spinner() : ''} | |
| </button> | |
| ${state === 'success' ? emoji.check : ''} | |
| </div> | |
| ` | |
| const service = { | |
| getData() { | |
| // return new Promise((res, rej) => setTimeout(rej, 1000)) | |
| return new Promise((res, rej) => setTimeout(res, 1000)) | |
| } | |
| } | |
| const machine = { | |
| dispatch(actionName, payload) { | |
| // const actions = this.transitions[this.state]; | |
| const action = this.transitions[this.state][actionName]; | |
| if (action) { | |
| console.log('Action dispatched', actionName, payload); | |
| action.apply(machine, payload); | |
| } | |
| }, | |
| changeStateTo(newState) { | |
| render(newState); | |
| this.state = newState; | |
| }, | |
| state: 'idle', | |
| transitions: { | |
| 'idle': { | |
| click() { | |
| this.changeStateTo('loading'); | |
| service.getData().then( | |
| data => { | |
| try { | |
| this.dispatch('success', data); | |
| } catch (error) { | |
| this.dispatch('failure', error) | |
| } | |
| }, | |
| error => this.dispatch('failure', error) | |
| ); | |
| } | |
| }, | |
| 'loading': { | |
| success(data) { | |
| this.changeStateTo('idle'); | |
| }, | |
| failure(error) { | |
| this.changeStateTo('error'); | |
| } | |
| }, | |
| 'error': { | |
| retry() { | |
| this.changeStateTo('idle'); | |
| this.dispatch('click'); | |
| } | |
| } | |
| } | |
| } | |
| ready(() => render(machine.state)); |
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