Why is it not possible to read data from req.body?

Question

Node.js

This piece of code worked and suddenly stopped working. I can't figure out what's the reason

router.post('/', function (req, res, next) {
    email.find({email: req.body.email}, function(err, data) {
        if(data[0].email === req.body.email) {
            res.send('Email exist!');
        } else {
            var dbData = new email({email: req.body.email});
            dbData.save(function (err, dbData, affected) {
                res.send(dbData);
                console.log(dbData);
            });
        }
    });
});

Application crashes with these logs

app-0 (entire): TypeError: Cannot read property 'email' of undefined
app-0 (entire):     at saveEmail (/var/www/app/routes/index.js:20:19)
app-0 (entire):     at Promise.<anonymous> (/var/www/app/routes/index.js:32:9)
app-0 (entire):     at Promise.<anonymous> (/var/www/app/node_modules/mongoose/node_modules/mpromise/lib/promise.js:177:8)
app-0 (entire):     at Promise.emit (events.js:95:17)
app-0 (entire):     at Promise.emit (/var/www/app/node_modules/mongoose/node_modules/mpromise/lib/promise.js:84:38)
app-0 (entire):     at Promise.fulfill (/var/www/app/node_modules/mongoose/node_modules/mpromise/lib/promise.js:97:20)
app-0 (entire):     at Object.cb (/var/www/app/node_modules/mongoose/lib/query.js:1010:22)
app-0 (entire):     at Object._onImmediate (/var/www/app/node_modules/mongoose/node_modules/mquery/lib/utils.js:137:16)
app-0 (entire):     at processImmediate [as _immediateCallback] (timers.js:354:15)

UPD
Do extra checks The logs complained about the non-existent email
property , only I was looking in the wrong place

email.find({email: req.body.email}, function(err, data) {
        if(data.length !== 0 && data[0].email === req.body.email) {
            res.send('Email exist!');
        } else {
            var dbData = new email({email: req.body.email});
            dbData.save(function (err, dbData, affected) {
                res.send(dbData);
                console.log(dbData);
            });
        }
    });

Answer 1

It's strange that it worked before and "suddenly" stopped working. In general, judging by the code, you are using expressjs. The documentation says expressjs.com/4x/api.html#req.body:
"req.body
Contains key-value pairs of data submitted in the request body. By default, it is undefined, and is populated when you use body- parsing middleware such as body-parser and multer."
That is, body is undefined by default and needs to be filled with something like body-parser.

Answer 2

Middleware needs to be inserted there, body-parser

Answer 3

can be written before routes app.use(express.urlencoded({extended: true}))