Global scope in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a global variable named count with value 10.

Javascript

var [1] = 10;

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

Acount

Blet

Cvar

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a keyword like 'let' or 'var' as the variable name.

Putting the value where the variable name should be.

The keyword var declares a variable, and count is the variable name. So var count = 10; creates a global variable named count with value 10.

2fill in blank

medium

Complete the code to access the global variable score inside the function and print it.

Javascript

var score = 5;
function showScore() {
  console.log([1]);
}
showScore();

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

Ascore

Bvar

Cconsole

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to redeclare the variable inside the function.

Using the keyword 'var' inside console.log.

The global variable score can be accessed inside the function by its name score. So console.log(score); prints the value 5.

3fill in blank

hard

Fix the error in the code so the global variable name is updated inside the function.

Javascript

var name = 'Alice';
function changeName() {
  [1] = 'Bob';
}
changeName();
console.log(name);

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

Alet name

Bconst name

Cvar name

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Redeclaring the variable inside the function with var, let, or const.

Trying to update the variable without assigning a value.

To update the global variable name, just assign a new value to name inside the function without redeclaring it. Using name = 'Bob'; changes the global variable.

4fill in blank

hard

Fill both blanks to create a global variable total and update it inside the function.

Javascript

[1] total = 0;
function addFive() {
  total [2]= 5;
}
addFive();
console.log(total);

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

Avar

B+

C+=

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using let instead of var for global variable declaration.

Using + instead of += inside the function.

var total = 0; declares a global variable. Inside the function, total += 5; adds 5 to the current value of total.

5fill in blank

hard

Fill all three blanks to create a global variable counter, increment it inside the function, and print it.

Javascript

[1] counter = 1;
function increment() {
  counter [2]= 1;
  console.log([3]);
}
increment();

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

Avar

Bcounter

C+=

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using let instead of var for global variable.

Using + instead of += for increment.

Printing a wrong variable name.

var counter = 1; declares a global variable. Inside the function, counter += 1; increases it by 1. Then console.log(counter); prints the updated value.

Practice

1. What does it mean when a variable is in the global scope in JavaScript?

easy

A. The variable can be accessed anywhere in the code.

B. The variable can only be used inside a function.

C. The variable is hidden from all parts of the code.

D. The variable is deleted after a function finishes.

Solution

1. Step 1: Understand global scope meaning

   Global scope means a variable is declared outside any function and is accessible everywhere in the code.

2. Step 2: Compare options with definition

   Only The variable can be accessed anywhere in the code. correctly states that the variable can be accessed anywhere.

3. Final Answer:

   The variable can be accessed anywhere in the code. -> Option A

4. Quick Check:

   Global scope = accessible everywhere [OK]

Hint: Global variables are outside functions, accessible everywhere [OK]

Common Mistakes:

• Thinking global variables are only inside functions
• Confusing global with local scope
• Believing global variables disappear after function ends

2. Which of the following is the correct way to declare a global variable in JavaScript?

easy

A. Inside a function using let

B. Outside any function using var

C. Inside a block using const

D. Inside a function using const

Solution

1. Step 1: Identify where to declare global variables

   Global variables must be declared outside any function or block.

2. Step 2: Check declaration keywords

   Using var outside functions creates a global variable. Options A, B, and D declare inside functions or blocks, so they are not global.

3. Final Answer:

   Outside any function using var -> Option B

4. Quick Check:

   Global variable = declared outside functions [OK]

Hint: Declare global variables outside functions with var [OK]

Common Mistakes:

• Declaring variables inside functions and expecting global scope
• Using let or const inside blocks thinking they are global
• Confusing block scope with global scope

3. What will be the output of this code?

var x = 10;
function show() {
  console.log(x);
}
show();

medium

A. 10

B. undefined

C. ReferenceError

D. null

Solution

1. Step 1: Identify variable scope

   Variable x is declared globally with var and has value 10.

2. Step 2: Check function access

   The function show logs x. Since x is global, it is accessible inside the function.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   Global variable accessed inside function = 10 [OK]

Hint: Global variables are accessible inside functions [OK]

Common Mistakes:

• Expecting undefined because variable is outside function
• Thinking console.log will cause ReferenceError
• Confusing local and global scope

4. Find the error in this code related to global scope:

function test() {
  var a = 5;
}
console.log(a);

medium

A. No error, prints 5

B. TypeError: a is undefined

C. ReferenceError: a is not defined

D. SyntaxError: var inside function

Solution

1. Step 1: Check variable scope

   Variable a is declared inside function test with var, so it is local to that function.

2. Step 2: Access variable outside function

   Trying to log a outside the function causes a ReferenceError because a is not in global scope.

3. Final Answer:

   ReferenceError: a is not defined -> Option C

4. Quick Check:

   Local variable accessed globally = ReferenceError [OK]

Hint: Variables inside functions are not global [OK]

Common Mistakes:

• Assuming var inside function is global
• Expecting output 5 instead of error
• Confusing ReferenceError with SyntaxError

5. You want to create a global counter variable that increases every time a function runs. Which code correctly uses global scope to do this?

hard

A. let counter = 0;
function count() {
let counter = 0;
counter++;
console.log(counter);
}

B. function count() {
var counter = 0;
counter++;
console.log(counter);
}

C. function count() {
let counter = 0;
counter++;
console.log(counter);
}

D. var counter = 0;
function count() {
counter++;
console.log(counter);
}

Solution

1. Step 1: Identify global variable declaration

   var counter = 0;
   function count() {
     counter++;
     console.log(counter);
   }

   declares counter outside the function, making it global and accessible inside the function.

2. Step 2: Check counter increment behavior

   Inside count, counter++ increases the global variable, so the count persists across calls.

3. Final Answer:

   var counter = 0; function count() { counter++; console.log(counter); } -> Option D

4. Quick Check:

   Global counter increments inside function =

   var counter = 0;
   function count() {
     counter++;
     console.log(counter);
   }

   [OK]

Hint: Declare counter outside function to keep it global [OK]

Common Mistakes:

• Declaring counter inside function resets it each call
• Using let inside function hides global variable
• Expecting local counter to remember previous value