map

map items of an iterable sequence to another value

Usage

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

Install

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

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

map(source, selector)

map() iterates the source and yields await selector(item, index)

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

selector(item, index) should return the object to yield. The second parameter is the index of the item as it appeared in the source sequence.

Example

example.js

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

async function main() {

  async function* source() {
    yield "hello"; yield "world";
  }

  let mapped = map(source(),
    (x, i) => {
      return {
        value: x.toString(),
        index: i
      }
    });

  for await (let item of mapped) {
    console.log(item);
  }
}

main();

Execute with the latest node.js:

node --harmony-async-iteration example.js

output:

{ value: 'hello', index: 0 }
{ value: 'world', index: 1 }

Typescript

This library is fully typed and can be imported using:

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

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

ts-node --harmony_async_iteration foo.ts