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Handmade Redux Demo
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>Handmade Redux Demo</title> | |
| </head> | |
| <body> | |
| <div> | |
| Counter: | |
| <span id="counter"></span> | |
| </div> | |
| <button id="inc"> | |
| Increment | |
| </button> | |
| <button id="dec"> | |
| Decrement | |
| </button> | |
| <!-- call javascript at the bottom of the page --> | |
| <script src="redux_demo.js"></script> | |
| </body> | |
| </html> |
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| let state = { | |
| counter: 0, | |
| }; | |
| const listeners = []; | |
| // create a new state based on the action passed | |
| function reducer(state, action) { | |
| switch (action) { | |
| case 'INC': | |
| return {...state, counter: state.counter + 1}; | |
| case 'DEC': | |
| return {...state, counter: state.counter - 1}; | |
| default: | |
| return state; | |
| } | |
| } | |
| function dispatch(action) { | |
| const newState = reducer(state, action); | |
| if (newState !== state) { | |
| state = newState; | |
| // notify all the listeners of the change | |
| listeners.forEach(listener => listener()); | |
| } | |
| } | |
| function subscribe(callback) { | |
| listeners.push(callback); | |
| } | |
| function updateView() { | |
| document.querySelector('#counter').innerText = state.counter; | |
| } | |
| subscribe(updateView); | |
| document.querySelector('#inc').onclick = () => dispatch('INC'); | |
| document.querySelector('#dec').onclick = () => dispatch('DEC'); | |
| // update view for the first time | |
| updateView(); |
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