@async-generators/filter

filter

filter an iterable sequence

Usage

package requires a system that supports async-iteration, either natively or via down-compiling

Install

npm install @async-generators/filter --save
yarn add @async-generators/filter

This package's main entry points to a commonjs distribution.

Additionally, the module entry points to a es2015 distribution, which can be used by build systems, such as webpack, to directly use es2015 modules.

Api

filter(source, predicate)

filter() iterates the source and yields any item where await predicate(item) === true

source must have a [Symbol.asyncIterator] or [Symbol.iterator] property. If both are present only [Symbol.asyncIterator] is used.

predicate(item, index) should return a boolean (optionally as Promise) to signal whether the item should be yielded. The second parameter is the index of the item as it appears in the source sequence.

Example

example.js

const filter = require('@async-generators/filter').default;

async function* source() {
  yield 1; yield 2; yield 3; yield 4;
}

async function main(){
  for await (let item of filter(source(), x=>x > 1 && x < 4)){
     console.log(item);
  }
}

main();

Execute with the latest node.js:

node --harmony-async-iteration example.js

output:

2
3

Typescript

This library is fully typed and can be imported using:

import filter from '@async-generators/filter');

It is also possible to directly execute your properly configured typescript with ts-node:

ts-node --harmony_async_iteration foo.ts