Functions – Scope

The area of code where a variable can be accessed; variables declared inside a function are local to it.

Part of: JavaScript Coding without HTML and CSS — Module 43, ACARA Digital Technologies Years 7–8 — Programming with Control Structures and Functions (JavaScript) — Module 65, ACARA Digital Technologies Years 9–10 — Modular and Object-Oriented Programming (JavaScript) — Module 16

Understanding Functions – Scope in JavaScript

What it does: scope describes exactly where a variable is visible and usable. Declaring with let inside a function scopes the variable to it. The variable only exists within that function's scope. Once the function ends, its local variables are gone. Variables in one function don't interfere with another function's variables. A variable must be declared before it can be used. Functions can access variables from the scope they were defined in. Once greet() finishes running, name no longer exists.

Common mistakes: msg is scoped inside say() and isn't accessible before or outside it. result is scoped inside add() and isn't accessible outside it.

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Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 41–52) and word search (Modules 21–52).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Does a variable declared with let inside a function stay local to it?

YesNo

Matches

function greet() { let name = "Sam"; } console.log(name);

↓

Wrong - name is scoped inside greet and isn't accessible outside it

Applying

Meanings

Term

scope

Meaning

The area of code where a variable can be accessed; variables declared inside a function are local to it.

Practice

function greet() {

Testing

Gaps

name = "Sam";

Check Answer

Spots

1console.log(msg);

2function say() {

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Quick Questions

1. Does a variable declared with let inside a function stay local to it?

A. Yes ✓

B. No

The variable only exists within that function's scope.

2. Can code outside a function access a variable declared inside it?

A. No ✓

B. Yes

Once the function ends, its local variables are gone.

3. Does each function create its own separate scope?

A. Yes ✓

B. No

Variables in one function don't interfere with another function's variables.

4. Can a variable be used before it's declared inside its own scope?

A. Yes

B. No ✓

A variable must be declared before it can be used.

5. Does calling a function twice create two separate variable scopes?

A. No

B. Yes ✓

Each call gets its own fresh copy of the function's local variables.

Match the Pairs

function greet() { let name = "Sam"; } → Declares name as a variable scoped inside greet

function calc() { let total = 10; return total; } → Declares total as a variable scoped inside calc

The area of code where a variable can be accessed → scope

Keeps a variable local so it can't be accessed outside its function → let count = 5;

function greet() { let name = "Sam"; } console.log(name); → Wrong - name is scoped inside greet and isn't accessible outside it

function calc() { let total = 5; } console.log(total); → Wrong - total is scoped inside calc and isn't accessible outside it

Key Term

scope

The area of code where a variable can be accessed; variables declared inside a function are local to it.

Fill in the Blanks

1. function greet() { let name = "Sam"; console.log(name); }

Hint: Type the keyword used to declare a local variable.

2. function calc() { let total = 10; return total; } console.log(calc());

Hint: Type the keyword that sends a value back out of the function.

3. function show() { let count = 5; console.log(count); }

Hint: Type the keyword used to declare a local variable.

4. function test() { if (true) { let x = 1; console.log(x); } }

Hint: Type the keyword used to declare a local variable.

5. function calcArea(side) { let area = side * side; return area; } console.log(calcArea(4));

Hint: Type the keyword that sends a value back out of the function.

Spot the Error

Question 1

A console.log(msg);

B function say() {

C let msg = "Hi";

D }

Line A — msg is scoped inside say() and isn't accessible before or outside it.

Question 2

A console.log(result);

B function add(a, b) {

C let result = a + b;

D return result;

E }

Line A — result is scoped inside add() and isn't accessible outside it.

Question 3

A function greet() {

B console.log(user);

C let user = "Amy";

D }

Line B — user is used before it's declared inside the function's scope.

Question 4

A function calcArea(s) {

B console.log(area);

C let area = s * s;

D return area;

E }

Line B — area is used before it's declared inside the function's scope.

Question 5

A function outer() {

B let x = 1;

C console.log(y);

D }

Line C — y was never declared anywhere in scope, so it can't be used.

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