Function expression in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a function expression in JavaScript?

A function expression is a way to define a function inside an expression, often assigned to a variable. It can be anonymous or named and is not hoisted like function declarations.

beginner

How do you assign a function expression to a variable?

You write: <code>const myFunc = function() { /* code */ };</code> This stores the function in the variable <code>myFunc</code>.

intermediate

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

Function declarations are hoisted, so you can call them before they appear in code. Function expressions are not hoisted, so you must define them before calling.

beginner

Can function expressions be anonymous? What does that mean?

Yes, function expressions can be anonymous, meaning they have no name. For example: <code>const f = function() { }</code>. The function has no name but is stored in <code>f</code>.

intermediate

How do arrow functions relate to function expressions?

Arrow functions are a shorter syntax for writing function expressions. For example: <code>const add = (a, b) => a + b;</code> is a function expression using arrow syntax.

Which of these is a valid function expression?

A const greet = function() { console.log('Hi'); };

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

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

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

Option A shows a function expression assigned to a variable. Option B is a function declaration.

What happens if you try to call a function expression before it is defined?

A It works fine because functions are hoisted.

B It calls the function but with empty parameters.

C It returns undefined.

D It causes an error because function expressions are not hoisted.

Function expressions are not hoisted, so calling them before definition causes an error.

Which is true about anonymous function expressions?

A They cannot be assigned to variables.

B They have no name and are often assigned to variables.

C They must have a name.

D They are hoisted like function declarations.

Anonymous functions have no name but can be stored in variables.

How do arrow functions differ from regular function expressions?

A Arrow functions must have names.

B Arrow functions are hoisted, regular ones are not.

C Arrow functions have a shorter syntax and do not have their own 'this'.

D Arrow functions cannot be assigned to variables.

Arrow functions use shorter syntax and do not have their own 'this' context.

Which keyword is used to assign a function expression to a variable?

A const or let

B var only

C function

D def

You use const or let to assign a function expression to a variable.

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

Think about when you can call the function in your code.

Describe how arrow functions relate to function expressions and mention one key difference.

Consider syntax and behavior differences.