Error Handling – try/catch

Runs code in a try block, and if an error occurs, runs the catch block instead of crashing.

Part of: JavaScript Coding without HTML and CSS — Module 44, ACARA Digital Technologies Years 9–10 — Modular and Object-Oriented Programming (JavaScript) — Module 42

Understanding Error Handling – try/catch in JavaScript

What it does: Errors in try are caught instead of stopping the whole program. The catch parameter stores details about what went wrong. The catch block runs instead of the program crashing. If no error occurs, the catch block is simply skipped. JavaScript is case-sensitive, so 'try' must be lowercase.

Common mistakes: 'try' must be lowercase - a capital T causes an error. 'console' is misspelled as 'consol'.

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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 try/catch let a program keep running after an error?

YesNo

Matches

Try { console.log(x); } catch (e) {}

↓

Wrong - 'try' must be lowercase

Applying

Meanings

Term

try...catch

Meaning

Runs code in a try block, and if an error occurs, runs the catch block instead of crashing.

Practice

try {

Testing

Gaps

{

Check Answer

Spots

1Try {

2console.log(a);

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Quick Questions

1. Does try/catch let a program keep running after an error?

A. Yes ✓

B. No

The catch block runs instead of the program crashing.

2. Does the catch block run only when an error occurs in try?

A. No

B. Yes ✓

If no error occurs, the catch block is simply skipped.

3. Must 'try' be written in lowercase?

A. Yes ✓

B. No

JavaScript is case-sensitive, so 'try' must be lowercase.

4. Must 'catch' be written in lowercase?

A. Yes ✓

B. No

JavaScript is case-sensitive, so 'catch' must be lowercase.

5. Does catch's parameter hold information about the error?

A. No

B. Yes ✓

The parameter, like e or error, stores details about what went wrong.

Match the Pairs

try { risky(); } catch (e) { ... } → Runs the try block, and if it errors, runs catch

catch (e) { console.log(e); } → Runs this block only if an error occurred in try

Prevents a program from crashing when an error occurs → try { risky(); } catch (e) {}

Holds information about the error inside catch → e

Try { console.log(x); } catch (e) {} → Wrong - 'try' must be lowercase

try { console.log(x); } Catch (e) {} → Wrong - 'catch' must be lowercase

Key Term

try...catch

Runs code in a try block, and if an error occurs, runs the catch block instead of crashing.

Fill in the Blanks

1. try { console.log(risky); } catch (e) { }

Hint: Type the keyword that starts the block of code to attempt.

2. try { doSomething(); } catch (e) { console.log(e); }

Hint: Type the keyword that runs its block only if an error occurs.

3. try { parseData(); } catch (err) { }

Hint: Type the parameter name that holds the error.

4. try { loadFile(); } catch (problem) { }

Hint: Type the keyword that starts the block of code to attempt.

5. try { connect(); } catch (problem) { console.log(problem); }

Hint: Type the keyword that runs its block only if an error occurs.

Spot the Error

Question 1

A Try {

B console.log(a);

C } catch (e) {

D }

Line A — 'try' must be lowercase - a capital T causes an error.

Question 2

A try {

B consol.log(b);

C } catch (e) {

D }

Line B — 'console' is misspelled as 'consol'.

Question 3

A try {

B console.log(c);

C } Catch (e) {

D }

Line C — 'catch' must be lowercase - a capital C causes an error.

Question 4

A try {

B console.log(d);

C } catch (e) {

D console.log(e)

E }

Line D — This line is missing a semicolon, but that's not required in JS.

Question 5

A try {

B console.log(g);

C } catch (e) {

D console.log(e);

E }}

Line E — There's an extra closing brace - only one } is needed here.

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