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Executing Async loop in sequence using Generator Functions in NodeJS
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| function* generatorFn(arr = [], asyncFn) { | |
| for(let item of arr) { | |
| // Alter this function according to your needs. | |
| // Also note that the below code would remain the same even in case of async-await functions | |
| yield asyncFn(item) | |
| } | |
| } | |
| async function execSequentially(arr, asyncFn) { | |
| let gen = generatorFn(arr, asyncFn) | |
| let result = gen.next(); | |
| while(!result.done) { | |
| let val = await result.value | |
| console.log(val) | |
| result = gen.next() | |
| } | |
| } | |
| function asyncFn(item){ | |
| // Random timeout is used just to confirm the true sequentialization of Async loop | |
| return new Promise(resolve => setTimeout(resolve, 1000 + 100, item)) | |
| } | |
| // This would go through the entire array creating a timeout for each item, | |
| // but would execute the timeout one-after-the-other (sequentially) | |
| execSequentially([123,2,3,4], asyncFn) |
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This solves the case where the code looks like below:
[1,2,3,4].forEach(async i => { await new Promise(resolve => setTimeout(resolve, Math.random() * 1000 + 100, item)) })If you execute the above code you may find different item being printed in unordered sequence.
But instead if you use the above
gist, then order would be sequential