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June 24, 2021 16:04
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Event observable
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function listen(fn) { | |
const gen = fn(); | |
function listener(ev) { | |
let { done } = gen.next(ev); | |
if(done) { | |
this.removeEventListener(ev.type, listener); | |
gen.return(); | |
} | |
} | |
return { listener }; | |
} | |
const subscription = listen(function*() { | |
let event; | |
while(event = yield) { | |
console.log('An event!', event); | |
} | |
}); | |
const el = document.querySelector('#btn'); | |
el.addEventListener('click', subscription.listener); |
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const obs = observable(); | |
obs.subscribe(function*() { | |
let event; | |
while(event = yield) { | |
console.log('An event!', event); | |
} | |
}); | |
const el = document.querySelector('#btn'); | |
el.addEventListener('click', obs.listener); | |
// Implementation | |
function observable() { | |
let observers = []; | |
function subscribe(fn) { | |
observers.push(fn()); | |
} | |
function listener(ev) { | |
for(let i = 0; i < observers.length; i++) { | |
let gen = observers[i]; | |
let { done } = gen.next(ev); | |
if(done) { | |
gen.return(); | |
observers.splice(i, 1); | |
i--; | |
} | |
} | |
if(observers.length === 0) { | |
this.removeEventListener(ev.type, listener); | |
} | |
} | |
return { listener, subscribe }; | |
} |
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