why is var mysql = require('mysql'); returning undefined

Question

EDITED:

I am working on a page that takes the information a user enters into a form and adds it to a database. I created the database with mysql. When trying to connect to my database using javascript. My code breaks on var mysql = require('mysql');:

I realized that this may be due to either the code being ran in a function or having the DOM related code in the function...

I tried running a simple version of the code without those elements and it works to connect to and update the database but I need to be able to pull the values from the form so I am still struggling with how to do this.

function saveUserForm() {
    var firstName = document.getElementById("firstName");
    var lastName = document.getElementById("lastName");
    var psw = document.getElementById("psw");
    var userName = document.getElementById("userName");
    var email = document.getElementById("inputText");
    alert('test');
    var mysql = require('mysql');
    alert("mysql test");
    var con = mysql.createConnection({
      host: "localhost",
      user: "root",
      password: "abc123",
      database: "PBSC_Parking_DB"
    });

    con.connect(function(err) {
     if (err){
         throw err;
         alert("error");
     }

    var sql = "INSERT INTO accounts (UserName, FirstName, LastName, Email, UserPassword) VALUES ('"+userName+ "', '"+firstName+"','"+lastName+"','"+email+"','"+psw+"')";

      con.query(sql, function (err, result) {
        if (err) {
            throw err;
            alert("test error");
        }
        alert("account added");
        console.log(result.affectedRows + " record(s) updated");
      });
    }); 
}

Please write the thrown error in your question. Undefined of what? — hurricane, Apr 16 '20 at 20:12
how does require() work in the same code as DOM commands? missing a tag? if using a client-side require, it's usually async and needs a callback or promise to access the imported values. — dandavis, Apr 16 '20 at 20:12
it doesn't say undefined of what... it just says 'undefined' i added at image of it for clarification — Alexandra Amara, Apr 16 '20 at 20:16

score 0 · Answer 1 · answered Apr 16 '20 at 20:19

0

you can try writing npm i mysql in the built in terminal of your ide instead of cmd and check that the mysql folder is added to your project dependencies or you can run npm i --g mysql to install that globally

answered Apr 16 '20 at 20:19

mohammadtz55

131
1
11

how do I check that it's added to my project dependencies? I did already try npm install mysql -g – Alexandra Amara Apr 16 '20 at 20:23
in the root folder of your project there is a folder called node_modules. check that folder the mysql folder should be there if its successfully installed – mohammadtz55 Apr 20 '20 at 08:10

score 0 · Answer 2 · answered Apr 16 '20 at 20:23

0

require('mysql') is async, so it needs to be treated as a promise. For safety, I would load this outside of the function scope. The only time you would need to require something inside the scope of a function is for lazy loading local assets.

answered Apr 16 '20 at 20:23

Raz Chiriac

406
2
7

I tried moving it outside the function and it still doesn't work – Alexandra Amara Apr 16 '20 at 20:29
Check this answer out, it might be what you need. https://stackoverflow.com/a/35390007/5326451 – Raz Chiriac Apr 16 '20 at 20:41

score 0 · Answer 3 · answered Apr 16 '20 at 20:40

0

You try to include a library with node from cmd so that's normal to give you undefined. cause node declares values like this. so you seem to install MySQL with npm globally. so it appears with you.

that's not related to your code at all. you need to produce bug in your code via log error or debug code!

answered Apr 16 '20 at 20:40

Omar Ghazi

161
3
7

it doesn't give an error... it just doesn't work. The alert doesn't alert on line 9 doesn't display is how i know it's breaking there. – Alexandra Amara Apr 16 '20 at 20:46
Cause you shouldn't use **document** in the backend. it's related to DOM [front-end] . so remove the first 8th lines from code then run the file – Omar Ghazi Apr 16 '20 at 20:52
I don't understand without document how I can pull the values from the form... but I tried taking them out for now and it still doesn't work. – Alexandra Amara Apr 16 '20 at 20:57

why is var mysql = require('mysql'); returning undefined

3 Answers3