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Signals experiment
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| <html> | |
| <body> | |
| <h1></h1> | |
| <button onclick="decrement()">-</button> | |
| <button onclick="increment()">+</button> | |
| <script> | |
| function signal(initial, callback = null) { | |
| let value = initial | |
| let subscribers = new Set(callback ? [callback] : []) | |
| return { | |
| get current() { | |
| return value | |
| }, | |
| set current(change) { | |
| value = change | |
| subscribers.forEach(callback => callback(value)) | |
| }, | |
| subscribe(callback) { | |
| subscribers.add(callback) | |
| return () => subscribers.delete(callback) | |
| } | |
| } | |
| } | |
| function computed(callback, dependencies) { | |
| const value = signal(callback()) | |
| dependencies.forEach(dependency => { | |
| dependency.subscribe(() => { | |
| value.current = callback() | |
| }) | |
| }) | |
| return value | |
| } | |
| /* this part would be generated from a compiler, similar to Svelte */ | |
| /* | |
| <script> | |
| let num = 0 | |
| @computed | |
| let double = num * 2 | |
| function increment() { | |
| num++ | |
| } | |
| function decrement() { | |
| num-- | |
| } | |
| <script> | |
| <h1>{double}</h1> | |
| <button onclick={decrement}>-</button> | |
| <button onclick={increment}>+</button> | |
| */ | |
| // let num = 0 | |
| // re-written by compiler to: | |
| let num = signal(0) | |
| // @computed | |
| // let double = num * 2 | |
| // re-written by compiler to: | |
| let double = computed(() => num.current * 2, [num]) | |
| // <h1>{double}</h1> | |
| // re-written by compiler to: | |
| const h1 = document.querySelector('h1') | |
| h1.textContent = double.current | |
| double.subscribe(() => { | |
| h1.textContent = double.current | |
| }) | |
| function increment() { | |
| // num++ | |
| // re-written by compiler to: | |
| num.current++ | |
| } | |
| function decrement() { | |
| // num-- | |
| // re-written by compiler to: | |
| num.current-- | |
| } | |
| </script> | |
| </body> | |
| </html> |
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