Created
September 16, 2018 13:56
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Very simple observable implementation
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function Observable(observe) { | |
this.map = f => { | |
return new Observable(cb => { | |
this.observe(x => { | |
cb(f(x)); | |
}); | |
}); | |
} | |
this.flatMap = f => { | |
return new Observable(cb => { | |
this.observe(x => { | |
f(x).observe(cb); | |
}); | |
}); | |
} | |
this.flatten = () => { | |
return this.flatMap(x => x); | |
} | |
this.zip = obs => { | |
var thisCur = undefined; | |
var otherCur = undefined; | |
return new Observable(cb => { | |
this.observe(x => { | |
thisCur = x; | |
cb([thisCur, otherCur]); | |
}); | |
obs.observe(x => { | |
otherCur = x; | |
cb([thisCur, otherCur]); | |
}) | |
}); | |
} | |
this.filter = f => { | |
return new Observable(cb => { | |
this.observe(x => { | |
if(f(x)) { | |
cb(x); | |
} | |
}) | |
}) | |
} | |
this.delay = t => { | |
return new Observable(cb => { | |
this.observe(x => { | |
window.setTimeout(() => { | |
cb(x); | |
}, t); | |
}); | |
}); | |
} | |
this.debounce = t => { | |
var lastHandle = undefined; | |
return new Observable(cb => { | |
this.observe(x => { | |
if(lastHandle !== undefined) { | |
clearTimeout(lastHandle); | |
} | |
lastHandle = window.setTimeout(() => { | |
cb(x); | |
}, t); | |
}); | |
}); | |
} | |
this.repeat = t => { | |
return new Observable(cb => { | |
this.observe(x => { | |
cb(x); | |
window.setInterval(() => { | |
cb(x); | |
}, t); | |
}); | |
}); | |
}; | |
this.fold = (f,z) => { | |
var curr = z; | |
return this.map(x => { | |
curr = f(curr,x); | |
return curr; | |
}) | |
} | |
this.observe = cb => { | |
var listening = true; | |
observe(x => { | |
if(listening) { | |
cb(x); | |
} | |
}); | |
return () => { | |
listening = false; | |
}; | |
} | |
} | |
Obs = { | |
from: x => { | |
return new Observable(cb => { | |
cb(x); | |
}) | |
}, | |
delayed: (x, time) => { | |
return Obs.from(x).delay(time); | |
}, | |
repeated: (x, time) => { | |
return Obs.from(x).repeat(time); | |
} | |
} | |
sequence = ls => { | |
if(ls.length === 0) { | |
return Obs.from([]); | |
} else { | |
return ls[0] | |
.zip(sequence(ls.splice(1))) | |
.map(l => [l[0]].concat(l[1])) | |
.filter(ls => ls.every(x => x !== undefined)); | |
} | |
} | |
fromEvent = (domElem, ev) => new Observable(cb => { | |
domElem.addEventListener(ev, (doc) => cb(doc)); | |
}); | |
var move = fromEvent(document, "mousemove"); | |
var t = move.debounce(300).fold((a,b) => a+1,0).observe(x => console.log(x)) |
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