如何将新的 Object 添加到空数组并在终端中显示

Question

Can anyone help me figure out how to add newUser Object to an empty array called users? The data I send using the POSTMAN inside of req.body is not displayed in the terminal when I run console.log(users)

   let users = [];
   app.post("/signup", (req, res) => {
     let username = req.body.username;
     let password = req.body.password;
     /* typeof and undefined is added for the scenario 
        if the request body has either username or password object only;
        OR any isn't declared in the request body. */

     if (username !== null &&
       username !== "" &&
       typeof username !== "undefined" &&
       password !== null &&
       password !== "" &&
       typeof password !== "undefined") {

       let requestBody = "";
       req.on("data", (addUser) => {
         requestBody += addUser;
       });
       req.on("end", () => {
         requestBody = JSON.parse(requestBody);
         let newUser = {
           "username": requestBody.username,
           "password": requestBody.password
         }
         users.push(newUser);
         console.log(users);
       });

       res.send(`User ${username} successfully registered`);
     } else {
       res.send(`Please input both username and password.`);
     }
   });

Answer 1

From the express documentation

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 express.json()

So you'll need to do this somewhere at the top of your file,

app.use(express.json);

Also, with express, you don't need to use req.on to parse incoming data, you can simply do the following,

   let users = [];
   app.post("/signup", (req, res) => {
     let username = req.body.username;
     let password = req.body.password;
     /* typeof and undefined is added for the scenario 
        if the request body has either username or password object only;
        OR any isn't declared in the request body. */

     if (username !== null &&
       username !== "" &&
       typeof username !== "undefined" &&
       password !== null &&
       password !== "" &&
       typeof password !== "undefined") {

       users.push({
         username,
         password
       });
       console.log(users);

       res.send(`User ${username} successfully registered`);
     } else {
       res.send(`Please input both username and password.`);
     }
   });

Here's your example on repl.it