Function parameters in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named greet that takes one parameter called name.

Javascript

function greet([1]) {
  console.log(`Hello, ${name}!`);
}

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

Amessage

Bname

Cgreeting

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than the one used inside the function.

Forgetting to add any parameter.

The function parameter should be named 'name' to match the usage inside the function.

2fill in blank

medium

Complete the code to call the function greet with the argument 'Alice'.

Javascript

greet([1]);

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

AAlice

B"Alice"

C'Alice'

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the string without quotes, which causes a reference error.

Using a variable name instead of a string.

When passing a string argument, it must be enclosed in quotes.

3fill in blank

hard

Fix the error in the function definition to correctly set a default value for the parameter age.

Javascript

function showAge(age [1] 18) {
  console.log(`Age is ${age}`);
}

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

A=

B==

C:

D=>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '=' for default parameters.

Using ':' or '=>' which are invalid here.

The correct syntax for default parameters uses a single equals sign '='.

4fill in blank

hard

Fill the three blanks to define a function multiply that takes two parameters and returns their product.

Javascript

function multiply([1], [2]) {
  return [1] [3] [2];
}

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

Aa

Bb

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong operator like '+' instead of '*'.

Mixing up parameter names.

The function parameters are 'a' and 'b', and the operator to multiply is '*'.

5fill in blank

hard

Fill both blanks to create a function that returns an object with keys as parameter names and values as their values.

Javascript

function createObject([1], [2]) {
  return { [1]: [1], [2]: [2] };
}

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

Ax

By

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for keys and values.

Forgetting to include both parameters.

The parameters are 'x' and 'y'. The object keys and values use the same names.

Practice

1.

What is the purpose of function parameters in JavaScript?

Choose the best explanation.

easy

A. They make functions run faster.

B. They create new functions automatically.

C. They stop a function from running.

D. They allow you to send information into functions to use inside.

Solution

1. Step 1: Understand what parameters do

   Parameters let you pass values into a function so it can use them inside.

2. Step 2: Evaluate the options

   Only "They allow you to send information into functions to use inside." correctly explains this purpose. Others describe unrelated or incorrect effects.

3. Final Answer:

   They allow you to send information into functions to use inside. -> Option D

4. Quick Check:

   Function parameters = input values [OK]

Hint: Parameters are inputs to functions, like filling a form [OK]

Common Mistakes:

• Thinking parameters create functions
• Believing parameters stop functions
• Assuming parameters speed up functions

2.

Which of the following is the correct way to define a function with two parameters a and b in JavaScript?

function add(???) { return a + b; }

easy

A. (a, b)

B. a b

C. a, b

D. [a, b]

Solution

1. Step 1: Recall function parameter syntax

   Parameters are listed separated by commas inside the function parentheses.

2. Step 2: Identify the correct parameter list

   (a, b) correctly lists parameters as 'a, b' inside parentheses. 'a, b' without parentheses is invalid syntax. Extra parentheses inside parentheses are not used.

3. Final Answer:

   (a, b) -> Option A

4. Quick Check:

   Parameters separated by commas inside () [OK]

Hint: List parameters separated by commas inside function parentheses [OK]

Common Mistakes:

• Using spaces instead of commas
• Adding extra parentheses around parameters
• Using brackets instead of commas

3.

What will be the output of this code?

function greet(name) {
  return `Hello, ${name}!`;
}
console.log(greet('Alice'));

medium

A. "Hello, Alice!"

B. "Hello, name!"

C. undefined

D. Error

Solution

1. Step 1: Understand function call with argument

   The function greet is called with 'Alice' as the argument for parameter name.

2. Step 2: Evaluate template literal output

   The template string inserts the value of name, so it becomes 'Hello, Alice!'.

3. Final Answer:

   "Hello, Alice!" -> Option A

4. Quick Check:

   Parameter value replaces placeholder [OK]

Hint: Parameter value replaces variable inside template strings [OK]

Common Mistakes:

• Thinking parameter name is printed literally
• Expecting undefined if parameter not used
• Confusing string quotes in output

4.

Find the error in this function definition:

function multiply(x, y) {
  return x * y;
}
multiply(5);

What will happen when multiply(5) is called?

medium

A. Throws a syntax error

B. Returns 25

C. Returns NaN

D. Returns 5

Solution

1. Step 1: Check function call with missing argument

   The function multiply expects two parameters but is called with only one argument (5).

2. Step 2: Understand behavior of missing parameter

   The second parameter y is undefined, so x * y becomes 5 * undefined, which results in NaN (Not a Number).

3. Final Answer:

   Returns NaN -> Option C

4. Quick Check:

   Missing argument causes NaN in math operations [OK]

Hint: Missing parameters become undefined, causing NaN in math [OK]

Common Mistakes:

• Expecting default value 0 for missing parameters
• Thinking it throws an error
• Assuming multiply returns the single argument

5.

Consider this function that uses default parameters:

function calculateTotal(price, tax = 0.1, discount = 0) {
  return price + price * tax - discount;
}
console.log(calculateTotal(100, undefined, 5));

What is the output of the console.log statement?

hard

A. 95

B. 105

C. 105.5

D. 105.0

Solution

1. Step 1: Understand default parameters and call

   The function has tax default 0.1 and discount default 0. The call passes price=100, tax=undefined, discount=5.

2. Step 2: Evaluate how undefined affects default

   Passing undefined for tax triggers the default value 0.1 to be used.

3. Step 3: Calculate the total

   Total = 100 + 100 * 0.1 - 5 = 100 + 10 - 5 = 105.

4. Final Answer:

   105 -> Option B

5. Quick Check:

   Undefined triggers default parameter value [OK]

Hint: Passing undefined uses default parameter value [OK]

Common Mistakes:

• Thinking undefined overrides default with undefined
• Ignoring discount in calculation
• Confusing tax and discount values