Sequentially load files

sequential-load.js

var loadedPromise,
    paths = [
      '//code.jquery.com/jquery-1.11.3.min.js',
      '//cdnjs.cloudflare.com/ajax/libs/jStorage/0.4.12/jstorage.min.js'
    ];

function simpleInclude(path) {
  return new Promise(function (resolve, reject) {
    var script = document.createElement('script');
    script.src = path;
    document.head.appendChild(script);
    script.onload = function() {
      resolve();
    };
  });
}

// Sequential loading.
loadedPromise = paths.reduce(function (previous, current) {
  return previous.then(function () {
    return simpleInclude(current);
  });
  // Initial promise to kick off the chain.
}, Promise.resolve(true));

@doublejosh noticed you have previous and current vars declared outside the function they're used in. That's unnecessary. Can just remove lines 2 & 3.