mirror of https://github.com/actions/setup-python
73 lines
1.7 KiB
Markdown
73 lines
1.7 KiB
Markdown
# p-reduce [](https://travis-ci.org/sindresorhus/p-reduce)
|
|
|
|
> Reduce a list of values using promises into a promise for a value
|
|
|
|
Useful when you need to calculate some accumulated value based on async resources.
|
|
|
|
|
|
## Install
|
|
|
|
```
|
|
$ npm install --save p-reduce
|
|
```
|
|
|
|
|
|
## Usage
|
|
|
|
```js
|
|
const pReduce = require('p-reduce');
|
|
const humanInfo = require('human-info'); // not a real module
|
|
|
|
const names = [
|
|
getUser('sindresorhus').then(info => info.name),
|
|
'Addy Osmani',
|
|
'Pascal Hartig',
|
|
'Stephen Sawchuk'
|
|
];
|
|
|
|
pReduce(names, (total, name) => {
|
|
return humanInfo(name).then(info => total + info.age);
|
|
}, 0).then(totalAge => {
|
|
console.log(totalAge);
|
|
//=> 125
|
|
});
|
|
```
|
|
|
|
|
|
## API
|
|
|
|
### pReduce(input, reducer, [initialValue])
|
|
|
|
Returns a `Promise` that is fulfilled when all promises in `input` and ones returned from `reducer` are fulfilled, or rejects if any of the promises reject. The fulfilled value is the result of the reduction.
|
|
|
|
#### input
|
|
|
|
Type: `Iterable<Promise|any>`
|
|
|
|
Iterated over serially in the `reducer` function.
|
|
|
|
#### reducer(previousValue, currentValue, index)
|
|
|
|
Type: `Function`
|
|
|
|
Expected to return a value. If a `Promise` is returned, it's awaited before continuing with the next iteration.
|
|
|
|
#### initialValue
|
|
|
|
Type: `any`
|
|
|
|
Value to use as `previousValue` in the first `reducer` invocation.
|
|
|
|
|
|
## Related
|
|
|
|
- [p-each-series](https://github.com/sindresorhus/p-each-series) - Iterate over promises serially
|
|
- [p-map-series](https://github.com/sindresorhus/p-map-series) - Map over promises serially
|
|
- [p-map](https://github.com/sindresorhus/p-map) - Map over promises concurrently
|
|
- [More…](https://github.com/sindresorhus/promise-fun)
|
|
|
|
|
|
## License
|
|
|
|
MIT © [Sindre Sorhus](https://sindresorhus.com)
|