co-reduce-any
v1.0.3
Published
Reduce anything in Co-like manner
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co-reduce-any
Reduce anything in Co-like manner
Provides a consistent interface for reducing arrays, strings, object literals, maps, sets, generators and streams. Synchronously whenever possible.
Installation
yarn add co-reduce-any
npm i -S co-reduce-any
Usage
reduce
behaves like Co, except
it's supplied with helper next
object. Yielding next
returns next
pair of the iteration or undefined
when there are no more elements.
Additionally if no promises were yielded, function returns by value. Always returns a promise when iterating over streams.
const reduce = require("co-reduce-any")
const collection = [ 1, 2, 3, 4 ]
reduce(collection, function* (next) {
const result = [ ]
for (let pair; pair = yield next;) {
const [ key, elem ] = pair
const value = yield Promise.resolve(elem * key)
result.push(value)
}
return result
}).then(result => console.log(result))
Key points:
value = yield promise // extract value from promise or throw, just like Co
yield next // waits for next [ key, element ] pair
What's the pair?
Pair is a 2-element array containing in order the key and the value of current element.
- In arrays and strings, key is the elements' index
- In ES6 Maps and object literals, key is the element's key
- In generators, ES6 Sets and node streams, key is the iteration's "i" provided for consistency
It's to preserve consistency with for...of
loop over ES6 Map. That
way you can write algorithms that work on any kind of collection.