81 lines
1.8 KiB
Markdown
81 lines
1.8 KiB
Markdown
# p-map-series [](https://travis-ci.org/sindresorhus/p-map-series)
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> Map over promises serially
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Useful as a side-effect mapper. Use [`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-map-series
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```
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## Usage
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```js
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const pMapSeries = require('p-map-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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let scores = [];
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const mapper = keyword => fetchScore(keyword).then(score => {
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scores.push(score);
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return {keyword, score};
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});
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pMapSeries(keywords, mapper).then(result => {
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console.log(result);
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/*
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[{
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keyword: 'unicorn',
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score: 99
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}, {
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keyword: 'rainbow',
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score: 70
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}, {
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keyword: 'pony',
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score: 79}
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]
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*/
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});
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```
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## API
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### pMapSeries(input, mapper)
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Returns a `Promise` that is fulfilled when all promises in `input` and ones returned from `mapper` are fulfilled, or rejects if any of the promises reject. The fulfilled value is an `Array` of the `mapper` created promises fulfillment values.
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#### input
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Type: `Iterable<Promise|any>`
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Mapped over serially in the `mapper` function.
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#### mapper(element, index)
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Type: `Function`
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Expected to return a value. If it's a `Promise`, it's awaited before continuing with the next iteration.
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## Related
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- [p-each-series](https://github.com/sindresorhus/p-each-series) - Iterate over promises serially
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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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