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JavaScript - how to make async loop class with next iteration confirmation?
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In this article, we're going to have a look at how to write own loop asynchronous class that uses callback functions to execute next iteration in proper time or break loop.
Note: read this article to see how to write async loop that executes next iterations in groups - when resources are available.
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// AsyncLoop class2
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function AsyncLoop(index, count, onStarted, onIteration, onFinished) {4
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var READY = 0;6
var EXECUTING = 1;7
var WAITING = 2;8
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var state = READY;10
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function resume() {12
if (state == EXECUTING) {13
if (index < count) {14
state = WAITING;15
var proxy = function() {16
state = EXECUTING;17
onIteration(index++, resume, finish);18
};19
setTimeout(proxy, 0);20
} else {21
state = READY;22
if (onFinished) {23
onFinished(true);24
}25
}26
}27
}28
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function finish() {30
if (state == EXECUTING) {31
state = READY;32
if (onFinished) {33
onFinished(false);34
}35
}36
}37
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this.run = function() {39
if (state == READY) {40
index = 0;41
if (onIteration.length > 1) {42
state = EXECUTING;43
if (onStarted) {44
onStarted();45
}46
resume();47
} else {48
if (onStarted) {49
onStarted();50
}51
while(index < count) {52
onIteration(index++);53
}54
if (onFinished) {55
onFinished(false);56
}57
}58
}59
};60
}61
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// Usage example:63
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function onStarted() {65
console.log('loop started');66
}67
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function onIteration(i, resume, finish) {69
console.log('loop iteration');70
setTimeout(resume, 500); // next iteration after 500ms71
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// resume() - continues loop73
// finish() - breaks loop74
}75
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function onFinished() {77
console.log('loop finished');78
}79
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var loop = new AsyncLoop(0, 5, onStarted, onIteration, onFinished);81
loop.run();