<a href="https://cnodejs.org/topic/542953d42ca9451e1bf3c251">拥抱Generator，告别异步回调</a>
var co = require('co');
co(function *(){
var now = Date.now();
yield sleep(500);
console.log(Date.now() - now);
})();
function sleep(ms){
return function(cb){
setTimeout(cb, ms);
};
}
