ie兼容promise
引入 <script src = "https://cdn.polyfill.io/v2/polyfill.min.js"></script>
或 <script type="text/javascript" src ="https://cdn.polyfill.io/v2/polyfill.min.js?features=es6"></script>
引入 <script src = "https://cdn.polyfill.io/v2/polyfill.min.js"></script>
或 <script type="text/javascript" src ="https://cdn.polyfill.io/v2/polyfill.min.js?features=es6"></script>