a-gist-test.js

var P = require('bluebird'); // 浏览器环境可忽略此行 http://bluebirdjs.com/docs/getting-started.html
var $e = $('.box');

P.each(['a', 'b', 'c'], function(html) {
  return P.delay(1000).then(function(){
    $e.html(html);
  });
}).then(function() {
  console.log('done');
});