js Async/AwaitierThe Awaitening

js Async/AwaitierThe Awaitening

by Chris Hiestand @dimmer

import _Isofetch from 'isomorphic-fetch';

async function getIp_P() {
    let ip = await fetch('https://api.ipify.org?format=json')
    .then((response) => {
        return response.json();
    });
    return ip;
}

function main() {
    [1,2,3].map(async () => {
        console.log('wan ip:');
        console.log(await getIp_P());
    });
}

main();

Output

wan ip:
wan ip:
wan ip:
{ ip: '1.2.3.4' }
{ ip: '1.2.3.4' }
{ ip: '1.2.3.4' }

See `async` think `Promise`

async function main() {
    return 'hello, wait for it, world';
}

console.log(main());

Output

Promise {
  _d:
   { p: [Circular],
     c: [],
     a: undefined,
     s: 1,
     d: true,
     v: 'hello, wait for it, world',
     h: false,
     n: true } }

Transpiled

var _asyncToGenerator2 = require('babel-runtime/helpers/asyncToGenerator');
var _asyncToGenerator3 = _interopRequireDefault(_asyncToGenerator2);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

let main = function () {
    var ref = (0, _asyncToGenerator3.default)(function* () {
        return 'hello, wait for it, world';
    });
    return function main() {
        return ref.apply(this, arguments);
    };
}();

console.log(main());

Promises return immediately but settle eventually

async function blah() {
    let foo = await doStuff_P();
    //more stuff
    return foo;
}

function main() {
    blah(); //returns promise immediately
}

Promise.map

import _Isofetch from 'isomorphic-fetch';
import _Promise from 'bluebird';

async function getIp_P() {
    let ip = await fetch('https://api.ipify.org?format=json')
    .then((response) => {
        return response.json();
    });
    return ip;
}

function main() {

    _Promise.map([1,2,3], async () => {
        console.log('wan ip:');
        console.log(await getIp_P());
    }, {concurrency: 1});
}

main();

Output

wan ip:
{ ip: '1.2.3.4' }
wan ip:
{ ip: '1.2.3.4' }
wan ip:
{ ip: '1.2.3.4' }

import _Isofetch from 'isomorphic-fetch';

async function getIp_P() {
    let ip = await fetch('https://api.ipify.org?format=json')
    .then((response) => {
        return response.json();
    });
    return ip;
}

async function main() {
    let i = 0;

    while( i < 3 ) {
        console.log('wan ip:');
        console.log(await getIp_P());
        i++;
    }
}

main();

Output

wan ip:
{ ip: '1.2.3.4' }
wan ip:
{ ip: '1.2.3.4' }
wan ip:
{ ip: '1.2.3.4' }

Summary

Async ⊧ Promise

Iterable + Async love with:

await Promise.map([1,2,3], remote_P)

Related blog post at: http://goo.gl/9J2S5V