Why the callback is not run

const wechatObj = new WechatJSSDK(config);
wechatObj.initialize()
  .then(w => {
    console.log('wechatObj w: ', w);//  **deos not run**
    //set up your share info, "w" is the same instance as "wechatObj"
  })
  .catch(err => {
    console.error(err);
  });

I only get this log 'Wechat script loaded successfully!'.
