Can I insert a function inside of a prompt? - node.js

Question

I'm trying to launch a really basic chat app for myself and a few friends and wanted to include a password check upon loading the site by using a prompt + socket.emit:
var username = prompt('password:');
socket.emit('password', password);
I wanted to insert a function that checks their input against whatever I define as the answer. Something like this:
var codeword = prompt('password:', function checkPrompt(password) {
if (prompt.password.length === 0) {
return false;
}
if (password.value !== answer.value) {
return false;
}
return true;
});
But I get ERR_INVALID_ARG_TYPE(name, 'Function', value); once I run the app. How can I implement this?
Sidenote: I know this is super insecure. I'll implement a real password check once I have a DB set up but until then I just wanted a simple placeholder.

Answer 1

prompt is a "blocking" method, so there is no need for a callback. Callbacks are needed when you are uncertain when code within the callback will be executed. This is not the case here. You can work with the returned result in a do...while loop for example.
Dummy example with static password check:
// We will keep the user in the loop until the password is correct...
do {
var password = prompt('Password:');
} while (password !== 'abcd');
// At this point we know the password was correct.
alert('Password was correct!');
Dummy example with dedicated auth method:
function authenticate(username, password) {
if (username == 'john' && password == 'abcd') {
return true;
}
return false;
}
// We will keep the user in the loop until the password is correct...
do {
var username = prompt('Username:');
var password = prompt('Password:');
var loginSuccessful = authenticate(username, password);
} while (!loginSuccessful);
// At this point we know the password was correct.
alert('Password was correct!');
From the security point of view, it only makes sense to have the authentication logic on server-side, so you'll most probably will want to make an AJAX call from within the above authenticate function (using the Fetch API for example or jQuery.post - if you're using jQuery). Then the method would return true or false based on the response of the server-side call.