Generator functions and promises

README.md

A quick demonstration of how Promises work with generator functions in ES6.

$ npm i
$ node_modules/.bin/babel-node promise-test.js

Output:

imaGenerator started
imaPromise started
imaPromise finished
resolving
imaGenerator yielding
ok

package.json

{
  "name": "promise-test",
  "version": "1.0.0",
  "description": "",
  "main": "promise-test.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "babel": "^5.5.8",
    "co": "^4.5.4"
  }
}

promise-test.js

import {co} from 'co';

function imaPromise() {
  console.log('imaPromise started');
  const p = new Promise(
    function (resolve, reject) {
      setTimeout(function () {
        console.log('resolving');
        resolve('ok');
      }, 1000);
    }
  );
  console.log('imaPromise finished');
  return p;
}

function *imaGenerator() {
  console.log('imaGenerator started');
  const v = yield imaPromise();
  console.log('imaGenerator yielding');
  return v;
}

co(function *() {
  const result = yield imaGenerator();
  console.log(result);
});