Promises, and loading the files

promiseAll.josh.js

function waitUp(t) {
  window.setTimeout(()=>console.log("waited", t),t)
}

waitUp.bind(null, 100)()  

function loadAFile(url) {
  return new Promise(function (resolve, reject){
    // simulate unknown wait time
    var delay = 1000*Math.random();
    window.setTimeout(function () {
      console.log('loaded', url);
      resolve();
    }, delay);

    // in the true one, you would call 
    // resolve from the onComplete, or such
  })
}

var log = {
  done: function () {console.log(Date.now(), "done")}
};


console.log("// this will wait until after load");
loadAFile('some.url').then(log.done);


function loadEmAll (names) {
  let promises = names.map(function (fn) {return loadAFile(fn)});
  return Promise.all(promises);
}

var fileNames = ['url1', 'url2', 'url3'];

loadEmAll(fileNames).then(log.done);
// or simpler!
Promise.all(fileNames.map(function (fn) {return loadAFile(fn)})).then(log.done);