Question

我正在为Facebook Messenger平台的聊天机器人工作，我发现了一个让我发疯的问题，因为我无法弄清楚为什么这是一个问题。

此代码正常运行。

app.post('/webhook', (req, res) => {

   let body = req.body;

   // Checks this is an event from a page subscription
   if (body.object === 'page') {

       // Iterates over each entry
       body.entry.forEach(function(entry) {

           // Gets the body of the webhook event
           let webhookEvent = entry.messaging[0];
           console.log(webhookEvent);

       });

       res.status(200).send('EVENT_RECEIVED');
   }
   else {
       // Returns a '404 Not Found'
       res.sendStatus(404);
   }

});

但最初，我想让function(entry)中的forEach成为 ES6箭头功能，例如：

body.entry.forEach((entry) => {

   // Gets the body of the webhook event
   let webhookEvent = entry.messaging[0];
   console.log(webhookEvent);
});

但登录控制台指出了这一点：

at body.entry.forEach (/app/src/app.js:57:41)
2017-12-19T15:10:08.768620+00:00 app[web.1]: TypeError: Cannot read property '0' of undefined
2017-12-19T15:10:08.768631+00:00 app[web.1]:     at Array.forEach (<anonymous>)
2017-12-19T15:10:08.768632+00:00 app[web.1]:     at app.post (/app/src/app.js:54:17)
2017-12-19T15:10:08.768634+00:00 app[web.1]:     at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
2017-12-19T15:10:08.768636+00:00 app[web.1]:     at next (/app/node_modules/express/lib/router/route.js:137:13)
2017-12-19T15:10:08.768637+00:00 app[web.1]:     at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3)
2017-12-19T15:10:08.768638+00:00 app[web.1]:     at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
2017-12-19T15:10:08.768638+00:00 app[web.1]:     at /app/node_modules/express/lib/router/index.js:281:22
2017-12-19T15:10:08.768639+00:00 app[web.1]:     at Function.process_params (/app/node_modules/express/lib/router/index.js:335:12)
2017-12-19T15:10:08.768640+00:00 app[web.1]:     at next (/app/node_modules/express/lib/router/index.js:275:10)

为什么这不适用于ES6箭头功能？

在forEach（）内的ES6箭头功能不起作用

0 个答案: