2019-06-13 23:44:43 +00:00
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# [batchasync.js](https://git.coolaj86.com/coolaj86/batchasync.js)
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2019-06-13 23:04:48 +00:00
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2019-06-13 23:47:27 +00:00
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Like calling `map()` and resolving with `Promise.all()`,
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but handling a bounded number of items at any given time.
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2019-06-13 23:44:43 +00:00
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2019-06-13 23:51:53 +00:00
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Want to read about it?
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- [Batching async requests in < 50 lines of VanillaJS](https://coolaj86.com/articles/batching-async-requests-50-lines-of-vanilla-js/)
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# Install
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2019-06-13 23:44:43 +00:00
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```bash
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npm install --save batchasync
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```
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2019-06-13 23:51:53 +00:00
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# Usage
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2019-06-13 23:44:43 +00:00
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```js
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// Browsers
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var batchAsync = window.batchAsync;
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```
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```js
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// Node
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var batchAsync = require('batchasync').batchAsync;
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```
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```js
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var batchSize = 4;
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var things = ['apples', 'bananas', 'pears'];
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function doStuff() {
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// ... go fetch things
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}
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batchAsync(batchSize, things, doStuff).then(function(results) {
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// all results, in order, just like Promise.all()
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console.log(results[0]);
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});
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```
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2019-06-14 16:52:27 +00:00
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## A note on `undefined`
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2019-06-13 23:51:53 +00:00
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Returning `undefined` will cause an exception to be thrown,
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and the Promise to be rejected.
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This is on purpose - because `undefined` is indistinguishable from a skipped Promise.
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2019-06-13 23:44:43 +00:00
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2019-06-13 23:51:53 +00:00
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Return `null` instead.
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2019-06-13 23:44:43 +00:00
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**Example (bad)**:
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```js
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function doStuff(thing) {
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// Oops! forgot to return
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request('https://searchallthe.pictures/api/' + thing);
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}
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```
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**Example (good)**:
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```js
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function doStuff(thing) {
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return request('https://searchallthe.pictures/api/' + thing);
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}
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```
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**Example (good)**:
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```js
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function doStuff(thing) {
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return null;
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}
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```
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