Function declaration in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a function declaration in JavaScript?

A function declaration defines a named function using the function keyword, followed by the function name, parentheses for parameters, and a block of code inside curly braces. It can be called anywhere in the code after or before its declaration.

beginner

How do you declare a function named greet that prints 'Hello!'?

You write: <pre>function greet() {<br>  console.log('Hello!');<br>}</pre>

intermediate

Can you call a function declared with a function declaration before it appears in the code?

Yes, function declarations are hoisted, so you can call them before their actual declaration in the code.

intermediate

What is the difference between a function declaration and a function expression?

A function declaration defines a named function and is hoisted, so it can be called before it appears. A function expression assigns a function to a variable and is not hoisted in the same way, so it can only be called after the assignment.

beginner

Write a function declaration named add that takes two numbers and returns their sum.

function add(a, b) {<br>  return a + b;<br>}

Which keyword is used to declare a function in JavaScript?

A func

B def

C function

D declare

The function keyword is used to declare functions in JavaScript.

What will happen if you call a function declared with a function declaration before its code appears?

A It works because function declarations are hoisted.

B It causes an error because the function is not defined yet.

C It returns undefined.

D It runs but with default parameters.

Function declarations are hoisted, so you can call them before their declaration.

Which of the following is a correct function declaration?

A function sayHi() { console.log('Hi'); }

B var sayHi = function() { console.log('Hi'); }

C sayHi = () => { console.log('Hi'); }

D def sayHi() { console.log('Hi'); }

Option A is a function declaration. Options B and C are function expressions or arrow functions. Option D is invalid in JavaScript.

What is the output of this code?<br>

function test() { return 5; }<br>console.log(test());

A Error

B 5

C undefined

D null

The function returns 5, so console.log prints 5.

Which statement about function declarations is TRUE?

A They are not hoisted.

B They cannot have parameters.

C They must be assigned to a variable.

D They can be called before they are declared in the code.

Function declarations are hoisted and can be called before their declaration.

Explain what a function declaration is and how it differs from a function expression.

Think about how you write the function and when you can call it.

Write a function declaration named multiply that takes two numbers and returns their product.

Use the function keyword and return the multiplication of the two inputs.