Aurelia preconditions for load

main.js

import * as DataServices from './data/services/index';

export function configure(aurelia) {
  aurelia.use
    .standardConfiguration()
    .developmentLogging();

  prestart(aurelia).then(
    ()  => start(aurelia),
    err => preconditionsFailed(err, aurelia)
  );
}

function prestart(aurelia) {
  let dataPromises = [];
  for (let serviceName in DataServices) {
    let serviceInstance = aurelia.container.get(DataServices[serviceName]);
    dataPromises.push(serviceInstance.loadInitialState());
  }

  return Promise.all(dataPromises);
}

function start(aurelia) {
  return aurelia.start().then(a => a.setRoot());
}

function preconditionsFailed(err, aurelia) {
  return Promise.resolve().then(() => {
    console.log("Failed to start due to failure during preconditions.", err);
    alert("Failed to start due to failure during preconditions.");
  })
}