Variable hoisting behavior in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable using var.

Javascript

console.log(x);
var [1] = 5;

Drag options to blanks, or click blank then click option'

Ax

By

Cz

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' or 'const' instead of 'var' here causes a ReferenceError when logging before declaration.

Declaring a different variable name than used in console.log.

The variable x is declared using var, which is hoisted and initialized to undefined.

2fill in blank

medium

Complete the code to show hoisting effect with var.

Javascript

console.log([1]);
var a = 10;

Drag options to blanks, or click blank then click option'

Ad

Ba

Cc

Db

Attempts:

3 left

💡 Hint

Common Mistakes

Logging a variable not declared with var causes ReferenceError.

Using a variable name different from the declared one.

Variable a is hoisted and initialized as undefined before assignment.

3fill in blank

hard

Complete the code to log the variable declared with let (this will cause an error).

Javascript

console.log([1]);
let b = 20;

Drag options to blanks, or click blank then click option'

Ab

Ba

Cc

Dd

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name different from the declared one.

Expecting var-like hoisting behavior with let.

Using let does not hoist the variable; accessing before declaration causes ReferenceError.

4fill in blank

hard

Fill both blanks to create a function that logs a hoisted variable.

Javascript

function test() {
  console.log([1]);
  var [2] = 30;
}
test();

Drag options to blanks, or click blank then click option'

Ax

By

Cz

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in console.log and declaration.

Using let or const instead of var for hoisting.

The variable x is hoisted inside the function and logs undefined.

5fill in blank

hard

Fill all three blanks to create a block with let and var variables and log the hoisted one.

Javascript

{
  var [1] = 40;
  let [2] = 50;
}
console.log([3]);

Drag options to blanks, or click blank then click option'

Aa

Bb

Cc

Dd

Attempts:

3 left

💡 Hint

Common Mistakes

Logging the let variable outside its block scope.

Using different variable names inconsistently.

Variable a declared with var is hoisted and accessible outside the block; b declared with let is block-scoped.