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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops A Closer Look At Loop Conditions

Posted by Laurence Foley
Laurence Foley
16,695 Points

Why is the following code not passing this treehouse challenge test?

The code works fine when I run it in my own browser but the challenge test doesn't pass it because it doesn't like me using a variable inside the while loop. Why?

app.js 
var password = "sesame";

  while(password !== secret) {
    var secret = prompt("What is the secret password?");
    if (secret === password) {
      document.write("You know the secret password. Welcome");
    } 
}
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript Loops</title>
</head>
<body>
<script src="app.js"></script>
</body>
</html>

1 Answer

Bryan Tidwell
Bryan Tidwell
3,473 Points 
var password = "sesame";
secret = prompt("What is the secret password?");

  while(password !== secret) {
    secret = prompt("What is the secret password?");
    if (secret === password) {

    } 
}

document.write("You know the secret password. Welcome");

This is all pretty new to me, but I managed to get it to work by duplicating the variable outside of the loop. I don't think you have to use the "var" to declare inside of a loop?

Additionally, you'll need to move your document.write command outside of the loop for it to display.

Bryan Tidwell
Bryan Tidwell
3,473 Points

But I'd love a comment from someone more experienced so we can both learn the "why" behind it. Thanks!

Oh, and I probably should have killed the "if" if I was going to move document.write. But it works!! I've got a lot to learn!

Bryan Tidwell
Bryan Tidwell
3,473 Points 
var password = "sesame";
var secret;

  while(password !== secret) {
    secret = prompt("What is the secret password?");
}

document.write("You know the secret password. Welcome");

There... cleaned it up a bit. That makes a little more sense to me, too. It declares the variable outside of the loop and kills the unnecessary "If". No reason for it. All we have to do is get the user to knock it out of the loop and we've already defined the string they have to type in.

William Li
William Li
Courses Plus Student 26,868 Points
William Li
William Li
Courses Plus Student 26,868 Points

hi, Bryan, the if conditional inside the while loop

    if (secret === password) {

    }

isn't doing anything here, you can just go ahead and delete it; other than that, the code looks pretty good to me.

Bryan Tidwell
Bryan Tidwell
3,473 Points

Thanks, William! I just figured that one out. So the only other question I've got is the variable. Can we not declare a new variable inside of a loop?

Oh, and many thanks to Laurence for letting me hijack his question and use it for own learning experience!

William Li
William Li
Courses Plus Student 26,868 Points
William Li
William Li
Courses Plus Student 26,868 Points 
while(password !== secret) {
    secret = prompt("What is the secret password?");
}

what you wrote is correct, don't put the var keyword, because inside the while loop, you aren't declaring the variable here, you're simply re-assigning a new value to it, the variable was previously declared outside of the loop.

Laurence Foley
Laurence Foley
16,695 Points

Thanks Bryan,

That looks alot better alright, but I'd still like to know why my orginal code was not passing.

Bryan Tidwell
Bryan Tidwell
3,473 Points

Absolutely, William. Thanks. But just to clarify, if I hadn't declared it before the loop, I couldn't do so inside it, correct?

And Laurence, I think the challenge was mainly upset with the "var" inside the loop and using the "if" as part of the solution. I've found with some of these challenges there are other ways to beat them, but sometimes only one or two solutions will work.

William Li
William Li
Courses Plus Student 26,868 Points
William Li
William Li
Courses Plus Student 26,868 Points

technically speaking, you could, because in Javascript, variable declared with var keyword doesn't not have block scope, and while loop is block scoped.

while(password !== secret) {
    var secret = prompt("What is the secret password?");
}

but the problem here is the while condition while(password !== secret), if you haven't declared the secret variable previously, when it gets to this line, JavaScript will raise an Exception error for undefined variable because it has no idea where secret comes from.

Bryan Tidwell
Bryan Tidwell
3,473 Points

Thanks! So much clearer now.