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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops Create a `do...while` loop

Posted by Catherine Kim
Catherine Kim
Courses Plus Student 7,498 Points

I ran this code in my browser and it works. Why doesn't it answer the challenge question

var secret = prompt("What is the secret password?");

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

}
document.write("You know the secret password. Welcome.");
script.js 
var secret = prompt("What is the secret password?");
do{

}
while ( secret !== "sesame" ) {
    secret = prompt("What is the 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="script.js"></script>
</body>
</html>
Justin Swatloski
Justin Swatloski
5,769 Points

The issue here is that you are prompting the user for an input, and once they put it in, the do loop does nothing, and will then continue to do nothing while the variable secret doesn't equal "sesame". Once it DOES equal sesame, you will be prompted for the secret again.

What your code should look like:

var secret;
do{
secret = prompt("What is the secret password?");
}
while ( secret !== "sesame" ) {
}
document.write("You know the secret password. Welcome.");

You first define the variable outside of the loop so that the do loop can use it for storage, then you execute the Do loop, which in this case will prompt the user for an input, and so long as that input does not equal "sesame", the do loop will keep repeating. Once it does equal sesame, it will go to the next line and write it.

Dave McFarland
Dave McFarland
Treehouse Teacher
Dave McFarland
Dave McFarland
Treehouse Teacher

Justin Swatloski

You don't need the second set of braces -- { } -- following the line with the while in it. The basic structure of a do...while loop is this:

do {
  // loop 
} while ( condition === true )

Of course, you replace the condition === true in my example above with the real condition you are testing.

1 Answer

Dave McFarland
STAFF
Dave McFarland
Treehouse Teacher
Dave McFarland
Dave McFarland
Treehouse Teacher

Hi, Catherine Kim

The basic structure of the do...while loop looks like this:

do {
  // the loop code goes in here
} while ( )

Because a do...while loop always runs at least once, you only need the prompt() method a single time: inside the loop. The prompt will appear once -- if the user provides the secret password then the while condition will be false and the loop exits. But if the answer is wrong, then the loop will run a second time, and the prompt will appear a second time. The prompt will appear again and again until the user types sesame.

I haven't given you the exact answer just a few hints -- try to see if you can solve this code challenge with just those hints.

Catherine Kim
Catherine Kim
Courses Plus Student 7,498 Points

Thanks Dave!