Block scope in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a block-scoped variable.

Javascript

function test() {
  [1] message = 'Hello';
  console.log(message);
}

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

Avar

Blet

Cconst

Dfunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' instead of 'let' causes the variable to be function-scoped.

Using 'function' keyword incorrectly to declare a variable.

The let keyword declares a block-scoped variable inside the function.

2fill in blank

medium

Complete the code to correctly access the block-scoped variable inside the block.

Javascript

if (true) {
  let [1] = 5;
  console.log(num);
}

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

Anum

Bnumber

Cvalue

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than declared causes a ReferenceError.

Trying to access the variable outside the block.

The variable declared with let is named num and accessible inside the block.

3fill in blank

hard

Fix the error by choosing the correct keyword to declare a block-scoped constant.

Javascript

if (true) {
  [1] PI = 3.14;
  console.log(PI);
}

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

Aconst

Blet

Cvar

Dfunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' or 'let' when the value should be constant.

Using 'function' keyword incorrectly.

const declares a block-scoped constant that cannot be reassigned.

4fill in blank

hard

Fill both blanks to create a block-scoped variable and check its scope.

Javascript

function checkScope() {
  [1] x = 10;
  if (true) {
    [2] x = 20;
    console.log(x);
  }
  console.log(x);
}

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

Alet

Bvar

Cconst

Dfunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using var for both variables causes the inner assignment to overwrite the outer.

Using const incorrectly when reassignment is needed.

The outer x is declared with var (function-scoped), and the inner x with let (block-scoped). The inner x shadows the outer inside the block.

5fill in blank

hard

Fill all three blanks to create a block-scoped variable, a constant, and print their values.

Javascript

function demo() {
  [1] name = 'Alice';
  if (true) {
    [2] greeting = 'Hello';
    [3](greeting + ', ' + name);
  }
}

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

Alet

Bconst

Cconsole.log

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using const for variables that are reassigned.

Forgetting to use console.log to print.

name is declared with var (function-scoped), greeting with let (block-scoped), and console.log prints the combined message.