Function execution context in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named greet.

Javascript

function [1]() {
  console.log('Hello!');
}

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

Ahello

BsayHello

Cgreet

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than 'greet'.

Forgetting to name the function.

The function name must be 'greet' to match the intended function definition.

2fill in blank

medium

Complete the code to call the function greet.

Javascript

[1]();

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

Agreet

BsayHello

Chello

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a function name that was not defined.

Forgetting the parentheses when calling the function.

To call the function named 'greet', use 'greet()'.

3fill in blank

hard

Fix the error in the function to correctly log the parameter.

Javascript

function greet(name) {
  console.log([1]);
}
greet('Alice');

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

AName

Bname

C'name'

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase 'Name' instead of 'name'.

Logging the string 'name' instead of the variable.

The parameter is named 'name' with lowercase, so use 'name' inside the function.

4fill in blank

hard

Fill both blanks to create a function that returns the sum of two numbers.

Javascript

function add([1], [2]) {
  return a + b;
}

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

Aa

Bb

Cx

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using parameter names that don't match the return statement.

Using unrelated variable names.

The function parameters must be 'a' and 'b' to match the return statement.

5fill in blank

hard

Fill all three blanks to create a function that checks if a number is positive.

Javascript

function isPositive([1]) {
  if (num [2] 0) {
    return [3];
  } else {
    return false;
  }
}

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

Anum

B>

Ctrue

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than 'num'.

Using '<' instead of '>' in the condition.

Returning false instead of true when the condition is met.

The parameter is 'num', the condition checks if num > 0, and returns true if so.

Practice

1. What does the function execution context in JavaScript primarily keep track of?

easy

A. Variables and parameters inside the function

B. The browser window size

C. The user's keyboard input globally

D. The network requests made by the page

Solution

1. Step 1: Understand what execution context means

   The function execution context is created when a function runs and it keeps track of what happens inside that function.

2. Step 2: Identify what is tracked inside the function

   It specifically keeps track of variables and parameters declared or passed inside the function.

3. Final Answer:

   Variables and parameters inside the function -> Option A

4. Quick Check:

   Execution context tracks variables and parameters [OK]

Hint: Execution context tracks function's own variables and parameters [OK]

Common Mistakes:

• Thinking it tracks global browser info
• Confusing with event listeners
• Assuming it tracks network requests

2. Which of the following is the correct way to define a function in JavaScript that creates a new execution context when called?

easy

A. var greet = 'Hi';

B. function greet() { console.log('Hi'); }

C. console.log('Hi');

D. if (true) { console.log('Hi'); }

Solution

1. Step 1: Identify function declaration syntax

   Only the syntax starting with the keyword function defines a function that creates an execution context when called.

2. Step 2: Check other options

   Options B, C, and D do not define functions; they are variable assignment or direct statements.

3. Final Answer:

   function greet() { console.log('Hi'); } -> Option B

4. Quick Check:

   Function declaration uses function keyword [OK]

Hint: Look for the 'function' keyword to define a function [OK]

Common Mistakes:

• Confusing variable assignment with function definition
• Thinking console.log alone defines a function
• Using if statement as a function

3. What will be the output of the following code?

function test() {
  let x = 5;
  return x + 3;
}
console.log(test());

medium

A. undefined

B. 5

C. 8

D. Error

Solution

1. Step 1: Analyze the function body

   The function test declares a variable x with value 5 inside its execution context.

2. Step 2: Calculate the return value

   The function returns x + 3, which is 5 + 3 = 8.

3. Final Answer:

   8 -> Option C

4. Quick Check:

   Return value is 5 + 3 = 8 [OK]

Hint: Add local variable and return value inside function [OK]

Common Mistakes:

• Confusing return value with variable value
• Expecting undefined because of missing global variable
• Thinking function does not return anything

4. Identify the error in the following code related to function execution context:

function add() {
  console.log(sum);
  let sum = 10 + 5;
}
add();

medium

A. TypeError because sum is not a function

B. No error, outputs 15

C. SyntaxError due to missing return statement

D. ReferenceError because 'sum' is used before declaration

Solution

1. Step 1: Understand variable hoisting with let

   Variables declared with let are not hoisted like var. Accessing them before declaration causes ReferenceError.

2. Step 2: Check the console.log usage

   The code tries to log sum before it is declared, causing ReferenceError.

3. Final Answer:

   ReferenceError because 'sum' is used before declaration -> Option D

4. Quick Check:

   Using let variable before declaration causes ReferenceError [OK]

Hint: Don't access let variables before declaration inside function [OK]

Common Mistakes:

• Assuming let variables are hoisted like var
• Expecting output 15 without error
• Confusing ReferenceError with SyntaxError

5. Consider this code:

function outer() {
  let a = 10;
  function inner() {
    let b = 20;
    return a + b;
  }
  return inner();
}
console.log(outer());

What does this example demonstrate about function execution contexts?

hard

A. Inner function can access variables of outer function's execution context

B. Inner function cannot access outer function variables

C. Outer function loses its execution context after returning

D. Variables declared in inner function are global

Solution

1. Step 1: Understand nested function execution contexts

   The inner function creates its own execution context but can access variables from the outer function's context due to closure.

2. Step 2: Analyze the return value

   The inner function returns a + b where a is from outer context and b is local, showing access to outer variables.

3. Final Answer:

   Inner function can access variables of outer function's execution context -> Option A

4. Quick Check:

   Closures allow inner functions to access outer variables [OK]

Hint: Inner functions access outer variables via closure [OK]

Common Mistakes:

• Thinking inner function variables are global
• Assuming outer context is lost immediately
• Believing inner cannot access outer variables