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

Posted by ori
ori
2,307 Points

Why is it not valid if I add a var inside the while loop?

I know the answer is: var secret = prompt("What is the secret password?");

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

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

But why can't I have it be: var secret = prompt("What is the secret password?");

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

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

In other words, why don't I call the var secret inside the while? Does it have to do with scope?

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

while ( secret !=== "sesame" ) {
  var 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="app.js"></script>
</body>
</html>

2 Answers

Ayoub AIT IKEN
Ayoub AIT IKEN
12,314 Points

hey there !

not in javascript only, it's in all languages, and David Brenecki its not about Treehouse, but you cant declare the same variable in and outside the loop. cause when you are typing the keyword " var " you are declaring a NEW variable and you are affecting a value to that variable, so if you reput the keyword " var " with the same name inside a loop, it will confuse the compiler system, since you are duplicating a variable, so either you declare a new variable with a new name, or you just use your variable without the keyword " var ".

PS : in this precise example, you can't declare a new variable, you d only use " secret = prompt(...) " , cause you need to check it's value each time the loop itirate !

cheers

kkswecpsyl
kkswecpsyl
8,155 Points

I'm talking about declaring it only inside the loop. Not both

ori
ori
2,307 Points

Thanks guys! Got it. Appreciate your help.

kkswecpsyl
kkswecpsyl
8,155 Points
kkswecpsyl
kkswecpsyl
8,155 Points

I think declaring a var in or outside a loop has to do with best coding practices and yes the scope. Declaring inside a loop a code block can still work but it is not optimized. If you get an error when declaring inside the loop its probably because Treehouse are trying to instill good coding practices into their students.

I think there are some cases though where declaring inside a loop is better