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65 lines
1.7 KiB
65 lines
1.7 KiB
# p-each-series [![Build Status](https://travis-ci.org/sindresorhus/p-each-series.svg?branch=master)](https://travis-ci.org/sindresorhus/p-each-series) |
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> Iterate over promises serially |
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Useful as a side-effect iterator. Prefer [`p-map`](https://github.com/sindresorhus/p-map) if you don't need side-effects, as it's concurrent. |
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## Install |
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``` |
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$ npm install --save p-each-series |
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``` |
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## Usage |
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```js |
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const pEachSeries = require('p-each-series'); |
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const keywords = [ |
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getTopKeyword() //=> Promise |
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'rainbow', |
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'pony' |
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]; |
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const iterator = el => saveToDiskPromise(el); //=> Promise |
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pEachSeries(keywords, iterator).then(result => { |
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console.log(result); |
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//=> ['unicorn', 'rainbow', 'pony'] |
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}); |
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``` |
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## API |
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### pEachSeries(input, iterator) |
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Returns a `Promise` that is fulfilled when all promises in `input` and ones returned from `iterator` are fulfilled, or rejects if any of the promises reject. The fulfillment value is the original `input`. |
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#### input |
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Type: `Iterable<Promise|any>` |
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Iterated over serially in the `iterator` function. |
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#### iterator(element, index) |
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Type: `Function` |
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Return value is ignored unless it's `Promise`, then it's awaited before continuing with the next iteration. |
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## Related |
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- [p-map-series](https://github.com/sindresorhus/p-map-series) - Map over promises serially |
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- [p-pipe](https://github.com/sindresorhus/p-pipe) - Compose promise-returning & async functions into a reusable pipeline |
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- [p-reduce](https://github.com/sindresorhus/p-reduce) - Reduce a list of values using promises into a promise for a value |
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- [p-map](https://github.com/sindresorhus/p-map) - Map over promises concurrently |
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- [More…](https://github.com/sindresorhus/promise-fun) |
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## License |
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MIT © [Sindre Sorhus](https://sindresorhus.com)
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