Why can the variable not be found here?

Question

It tells me variable secret can not be found.

// Display the prompt dialogue while the value assigned to `secret` is not equal to "sesame"
do {
  let secret = prompt("What is the secret password?");
} while ( secret !== "sesame");
// This should run after the loop is done executing
alert("You know the secret password. Welcome!");

`let` has a strict scoping rule: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let — Greedo, Jul 30 '20 at 15:13
``do { var secret = prompt("What is the secret password?"); } while ( secret !== "sesame");`` — henok, Jul 30 '20 at 15:15
Does this answer your question? [What's the difference between using "let" and "var"?](https://stackoverflow.com/questions/762011/whats-the-difference-between-using-let-and-var) — Vishesh Mangla, Jul 30 '20 at 15:46

Vishesh Mangla · Answer 1 · 2020-07-30T15:43:14.853

1

let has block scope. Use const or var.

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

EDIT: On suggestion of @James

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

will work too since now let's scope is increased by defining it out of do while statement's block

edited Jul 30 '20 at 15:43

answered Jul 30 '20 at 15:15

Vishesh Mangla

664
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Since you moved the declaration outside the block, you could also use `let` here, but `const` will not work since you are redefining the variable with the prompt response. – James Jul 30 '20 at 15:38

Amel · Answer 2 · 2020-07-30T20:05:31.010

0

Like other people already commented: let has a strict scoping rule. Use var or const instead. Or use let outside the block, one level higher.

edited Jul 30 '20 at 20:05

answered Jul 30 '20 at 15:40

Amel

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9
15

Do not use const. – James Jul 30 '20 at 15:40

Why can the variable not be found here?

2 Answers2