如何在Express.js中将回调放入res.json

Question

I need to call asynchronous callback function that return object in my Express.js, but I don't know how!

app.get('/first', function (req, res, next) {

res.json(//put my async callback function here ?);
});

The function:

const reqObj = () => {
  request(`isdb.pw/${url}`, function(err, res, body) {
    if (!err) {
      const $ = cheerio.load(body);
      var name = $('meta[name="description"]').attr('content');
      var story = $('meta[property="og:video:url"]').attr('content');
      return {
        name,
        story
      };
    } else {
      console.log(err);
    }
  });
};

Answer 1

First, make the function return a Promise, then you can use .then on it:

const reqObj = () => {
  return new Promise((resolve, reject) => {
    request(`isdb.pw/${url}`, function(err, res, body) {
      if (!err) {
        const $ = cheerio.load(body);
        var name = $('meta[name="description"]').attr('content');
        var story = $('meta[property="og:video:url"]').attr('content');
        resolve({
          name,
          story
        });
      } else {
        reject(err);
      }
    });
  });
};

After that call the asynchronous function and run res.json() once you have the data:

app.get('/first', function (req, res, next) {
  reqObj().then(data => {
    res.json(data);
  }).catch(err => console.log(err)); 
});

res.json() only accepts Objects as it's parameter

---

Here is a solution with callbacks

 const reqObj = (callback) => { // <-- add callback parameter here request(`isdb.pw/${url}`, function(err, res, body) { if (!err) { const $ = cheerio.load(body); var name = $('meta[name="description"]').attr('content'); var story = $('meta[property="og:video:url"]').attr('content'); callback(null,{ // <-- call callback function without err, but with data name, story }); } else { callback(err); // <-- call callback just with data } }); }); }; app.get('/first', function(req, res, next) { reqObj((err, data) => { // <-- pass callback function if(err) return console.log(err) // <-- check for error res.json(data); }); });