Function scope in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is function scope in JavaScript?

Function scope means variables declared inside a function can only be used within that function. They are hidden from the outside world.

beginner

What happens if you try to access a variable declared inside a function from outside that function?

You get a ReferenceError because the variable only exists inside the function's scope.

beginner

Consider this code:<br><pre>function greet() {<br>  let message = 'Hi!';<br>  console.log(message);<br>}<br>greet();<br>console.log(message);</pre><br>What will happen when running it?

The function prints 'Hi!'. But the last line causes an error because message is not visible outside the function.

beginner

Can variables declared with var inside a function be accessed outside the function?

No. Variables declared with var inside a function are also limited to that function's scope.

intermediate

What is the difference between function scope and block scope?

Function scope limits variables to the whole function. Block scope limits variables to the block (like inside {}) where they are declared, usually with let or const.

Where can a variable declared inside a function be accessed?

A Only inside that function

B Anywhere in the program

C Only inside loops

D Only inside if statements

Variables declared inside a function are only accessible within that function's scope.

What will happen if you try to access a function-scoped variable outside its function?

A It will return the variable's value

B It will create a new variable

C It will print null

D It will cause a <code>ReferenceError</code>

Function-scoped variables are not visible outside their function, so accessing them outside causes a ReferenceError.

Which keyword creates a variable with function scope?

A var

B const

C let

D function

var declares variables with function scope.

What is the scope of a variable declared with let inside a function?

A Global scope

B Function scope

C Block scope inside the function

D No scope

let variables have block scope, so inside a function they are limited to the block they are declared in.

Which of these is true about function scope?

A Variables declared inside a function are accessible outside it

B Variables declared inside a function are hidden from outside

C Function scope only applies to global variables

D Function scope is the same as block scope

Function scope hides variables declared inside a function from outside access.

Explain function scope in JavaScript and how it controls variable visibility.

Think about where you can use variables declared inside a function.

Describe the difference between function scope and block scope with examples.

Consider how variables behave inside functions and inside blocks like if or loops.