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JavaScript - how to make async loop that continues iteration when is ready in modern js?
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In this article, we're going to have a look at how to write own asynchronous loop that executes next iteration in proper time or breaks loop.
Note: read this article to see how to write async loop that executes next iterations on calling callback function - this approach is recommended with old JavaScript.
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// async loop method2
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let sleepLoop = async (milliseconds) => {4
var promise = new Promise((resolve, reject) => {5
setTimeout(resolve, milliseconds);6
});7
return promise;8
};9
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let runLoop = async (onStarted, onIteration, onFinished) => {11
await onStarted();12
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for (var i = 0; i < 5; ++i) {14
var result = await onIteration(i);15
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if (result === false) {17
break;18
}19
}20
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await onFinished();22
};23
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// Helpers utils:25
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class Timer {27
constructor() {28
this.t1 = new Date();29
}30
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getTime() {32
let t2 = new Date();33
return t2 - this.t1;34
}35
}36
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let timer = new Timer();38
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let printMessage = (message) => {40
console.log('[' + message + ', time=' + timer.getTime() + ']');41
};42
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// Usage example:44
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let onStarted = async () => {46
printMessage('loop started');47
};48
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let onIteration = async (i) => {50
printMessage('loop iteration');51
await sleepLoop(500); // next iteration after 500ms52
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//return false; // true - keeps loop execution, false - breaks loop execution54
};55
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let onFinished = async (i) => {57
printMessage('loop finished');58
};59
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runLoop(onStarted, onIteration, onFinished);
