BudiBaduQuiziBadu

JavaScript Basic Error Types (SyntaxError, TypeError) Quiz

JavaScript
0 Passed
0% acceptance

Explore 40 JavaScript questions covering SyntaxError definitions, parsing mistakes, prevention strategies, TypeError causes, undefined versus null access issues, strict mode implications, debugging stacks, try/catch usage, and best practices for runtime resilience.

40 Questions
~80 minutes
1

Question 1

What is a SyntaxError in JavaScript?

A
An error thrown when code cannot be parsed according to language grammar
B
Any error caused by network failures
C
A runtime type mismatch
D
An unused variable warning
2

Question 2

Which situation commonly triggers a SyntaxError?

A
Forgetting a closing parenthesis or bracket
B
Dividing by zero
C
Accessing a property on undefined
D
Calling a function with the wrong arguments
3

Question 3

What does the following code throw?

javascript
function greet(
  console.log('hi')
}
A
SyntaxError
B
TypeError
C
ReferenceError
D
No error
4

Question 4

How does the JS engine decide to throw a SyntaxError?

A
During parsing when tokens violate grammar rules
B
Only after code executes in the browser
C
Whenever a promise rejects
D
When the call stack exceeds its limit
5

Question 5

Which tool helps prevent SyntaxErrors before running code?

A
A linting and formatting pipeline
B
A production error boundary
C
Service worker caching
D
setTimeout
6

Question 6

Why does using a reserved word as a variable name cause a SyntaxError?

A
Because reserved words have fixed grammatical meaning in the language
B
Because the variable is undefined
C
Because the variable is const
D
Because the code runs slowly
7

Question 7

Which practice reduces SyntaxErrors when writing large objects?

A
Trailing commas and consistent indentation
B
Relying on eval
C
Inlining all strings
D
Disabling formatting tools
8

Question 8

What error occurs when you run this snippet?

javascript
const data = JSON.parse('{ name: "Pat" }')
A
SyntaxError
B
TypeError
C
ReferenceError
D
RangeError
9

Question 9

Identify the outcome:

javascript
let x = 0
if (x === 0)
  console.log('zero')
  console.log('done')
A
SyntaxError due to ambiguous block
B
Only the first log runs
C
Both logs conditionally run
D
TypeError
10

Question 10

Which preventive step best avoids SyntaxErrors in template literals?

A
Using ESLint rules that flag unmatched ${ } sequences
B
Disabling template literals
C
Switching to string concatenation only
D
Wrapping every literal in eval
11

Question 11

What is a TypeError?

A
An error thrown when an operation is performed on the wrong kind of value
B
A syntax-level parsing failure
C
A networking timeout
D
A CSS validation issue
12

Question 12

What happens when this code executes?

javascript
const tools = undefined
tools.forEach(t => console.log(t))
A
TypeError: Cannot read properties of undefined
B
SyntaxError
C
No output but no error
D
ReferenceError
13

Question 13

Which scenario commonly causes a TypeError involving null?

A
Accessing a property on null without checking its value
B
Declaring a const variable
C
Writing a template literal
D
Importing a module twice
14

Question 14

What is a good strategy to prevent undefined vs null access errors?

A
Use optional chaining or early return guards before property access
B
Always convert everything to strings
C
Disable strict mode
D
Rely on implicit globals
15

Question 15

Which TypeError occurs when calling something that is not a function?

A
"is not a function"
B
"Unexpected identifier"
C
"Unexpected token"
D
"Illegal break"
16

Question 16

How does strict mode affect assignment to undeclared variables?

A
It throws a ReferenceError instead of creating an implicit global
B
It logs a warning only
C
It silently creates a var
D
It converts the value to string
17

Question 17

What happens in strict mode here?

javascript
'use strict'
function demo() {
  sloppyVar = 10
}
demo()
A
ReferenceError: sloppyVar is not defined
B
TypeError
C
SyntaxError
D
No error
18

Question 18

Which strict mode rule helps prevent silent TypeErrors?

A
Disallowing duplicate parameter names
B
Requiring semicolons
C
Forcing camelCase variable names
D
Blocking template literals
19

Question 19

Evaluate the outcome:

javascript
const settings = null
console.log(settings.theme)
A
TypeError: Cannot read properties of null
B
SyntaxError
C
Logs undefined
D
ReferenceError
20

Question 20

Which TypeError stems from invalid function invocation?

A
Calling array.length() as if it were a function
B
Using JSON.parse
C
Writing a for loop
D
Declaring const
21

Question 21

What does an error stack trace provide?

A
The call sequence leading to the error
B
Browser cache contents
C
Network latency
D
Package versions
22

Question 22

What does this snippet output?

javascript
try {
  throw new TypeError('Bad input')
} catch (err) {
  console.log(err instanceof TypeError)
}
A
true
B
false
C
TypeError
D
SyntaxError
23

Question 23

What is a good reason to rethrow an error inside catch?

A
To surface the issue after adding context or logging
B
To silence all errors globally
C
To convert TypeErrors into SyntaxErrors
D
To warm up the JIT compiler
24

Question 24

Analyze the behavior:

javascript
try {
  JSON.parse('{ invalid }')
} catch (err) {
  console.error('Failed:', err.message)
} finally {
  console.log('Cleanup')
}
A
Logs the error message and then "Cleanup"
B
Throws unhandled SyntaxError
C
Skips finally
D
Never executes catch
25

Question 25

How can you create a custom error message for a validation failure?

javascript
class ValidationError extends Error {
  constructor(field) {
    super(`${field} is required`)
    this.name = 'ValidationError'
  }
}
throw new ValidationError('email')
A
By subclassing Error and supplying a message in super
B
By overriding JSON.stringify
C
By editing console.log
D
By disabling strict mode
26

Question 26

Which error occurs when reading property "length" on a number?

A
Undefined returns undefined; no error
B
TypeError if you try to assign length
C
SyntaxError
D
RangeError
27

Question 27

What does this log?

javascript
const count = 5
count()
console.log('done')
A
TypeError: count is not a function
B
5
C
done
D
SyntaxError
28

Question 28

How can optional chaining reduce TypeErrors?

A
By returning undefined instead of throwing when accessing deep properties
B
By converting all values to strings
C
By disabling strict mode
D
By forcing synchronous code
29

Question 29

Which best practice avoids property access on non-objects?

A
Validate inputs and bail early if they are not objects
B
Rely on implicit coercion to convert types
C
Mutate built-in prototypes
D
Catch all errors and ignore them
30

Question 30

Why is property access on undefined a TypeError rather than SyntaxError?

javascript
function printUser(user) {
  console.log(user.name)
}
printUser(undefined)
A
Because the syntax is valid but the operation fails at runtime
B
Because undefined is a reserved word
C
Because undefined values cannot be declared
D
Because TypeError rules execute before parsing
31

Question 31

When is try/catch most appropriate?

A
When you expect a block of code may throw and you need to recover gracefully
B
For every function regardless of behavior
C
To replace validation logic
D
Only inside event handlers
32

Question 32

How can custom error messages aid debugging?

A
They tell future developers exactly what went wrong and how to fix it
B
They reduce bundle size
C
They eliminate the need for console logging
D
They convert SyntaxErrors into TypeErrors
33

Question 33

Which try/catch pattern is considered an anti-pattern?

javascript
try {
  // thousands of lines of unrelated logic
} catch (err) {
  // ignore all errors
}
A
Wrapping massive code blocks and catching all errors without handling them
B
Catching specific known failures
C
Logging and rethrowing
D
Using finally for cleanup
34

Question 34

How does using finally help when handling TypeErrors?

A
It guarantees cleanup steps run regardless of success or failure
B
It prevents TypeErrors from being thrown
C
It converts TypeErrors to SyntaxErrors
D
It only executes if no error occurs
35

Question 35

Why should custom errors extend Error instead of plain objects?

A
Extending Error preserves stack traces and instanceof checks
B
Plain objects cannot be thrown
C
Plain objects are prohibited in strict mode
D
Extending Error shortens bundle size
36

Question 36

How can source maps help when debugging SyntaxErrors in minified code?

A
They map minified positions back to original files and line numbers
B
They automatically fix the error
C
They disable minification
D
They wrap code in try/catch
37

Question 37

What benefit does enabling Break on Exceptions in dev tools provide?

A
It pauses execution exactly where the error occurs
B
It rewrites the code to avoid errors
C
It minifies scripts further
D
It forces strict mode
38

Question 38

How can logging err.stack be useful when sharing bug reports?

A
It provides call-site context for remote teammates
B
It redacts sensitive data automatically
C
It prevents the error
D
It speeds up the runtime
39

Question 39

Which statement about window.onerror is accurate?

A
It captures uncaught errors, enabling centralized logging
B
It prevents SyntaxErrors during parsing
C
It only runs on mobile browsers
D
It replaces try/catch entirely
40

Question 40

What best practice helps align SyntaxError and TypeError handling?

A
Combine automated tests, linting, and descriptive runtime guards
B
Disable all tooling to avoid slowdowns
C
Swallow every error silently
D
Use eval to dynamically rewrite code

Other Quiz Categories

Rust
30 quizzes
Cargo and Project Setup
Variables and Mutability
Data Types
Python
29 quizzes
Introduction & Core Fundamentals
Data Types Overview
Type Casting
Golang
29 quizzes
Basics & Syntax
Data Types & Zero Values
Operators & Expressions
C++
26 quizzes
Basics
Variables & Data Types
Operators & Expression
Java
22 quizzes
Java Basics & JVM Fundamentals
Variables, Data Types & Type Casting
Operators & Expressions
Matlab
21 quizzes
Basics & Environment
Variables and Data Type
Arrays and Matric
TypeScript
19 quizzes
Introduction and Overview
Installation and Configuration
Basic Types and Type Annotations
SQL Database
15 quizzes
Foundations and Basics
Basic Query Selection
Filter, Sort, and Alias Essentials
PHP
15 quizzes
Syntax Building Blocks
Variable Naming
Data Types Overview
Linked List
11 quizzes
Introduction
Node Structure and Pointer Fundamentals
Singly Linked List

QUIZZES IN JavaScript

1

Basics

40

A beginner-friendly quiz to evaluate your understanding of core JavaScript fundamentals including variables, data types, operators, and foundational syntax. This quiz builds the base for mastering more advanced JavaScript concepts.

2

Variables & Data Types

50

A focused JavaScript quiz dedicated to variables, scope, primitive values, reference types, and type conversion. Use this set to check how well you understand declarations, assignments, comparison rules, and everyday runtime behaviour.

3

Operators & Expressions

50

A detailed JavaScript quiz exploring arithmetic, comparison, logical, bitwise, and assignment operators through practical expressions and tricky evaluation scenarios.

4

Strings & String Methods

75

Tackle 75 JavaScript string challenges that cover formatting, slicing, searching, pattern matching, and Unicode-safe manipulation to solidify everyday text-processing skills.

5

Numbers & Math Operations

75

Master 75 JavaScript questions that cover numeric literals, parsing, formatting, math utilities, and the edge cases every engineer hits when working with numbers.

6

Arrays & Basic Array Methods

100

Tackle 100 JavaScript array questions that range from everyday indexing to tricky splice mutations and iteration strategies. Forty questions supply runnable code so you can reason through exact behaviour before answering.

7

Objects & Key/Value Manipulation

75

Explore 75 JavaScript object questions that cover construction, property access, mutation, introspection, cloning, and immutability. Thirty questions include runnable snippets so you can reason through exact behaviour before answering.

8

Control Flow (if, else, switch)

50

Explore 50 JavaScript control-flow questions covering branching, truthiness, equality pitfalls, nested decisions, switch mechanics, fallthrough, and short-circuit expressions. Twenty questions include runnable snippets so you can reason about exact evaluation before answering.

9

Functions & Parameters

50

Explore 50 JavaScript function questions covering declarations, expressions, arrow functions, scopes, parameters, defaults, rest arguments, return values, closures, and execution flow.

10

Boolean Logic & Truthy/Falsy

50

Explore 50 JavaScript questions covering boolean values, logical operators, comparison pitfalls, truthy/falsy coercion, short-circuit flow, optional chaining, nullish coalescing, ternaries, and real-world conditional patterns.

11

Type Conversion & Coercion

50

Explore 50 JavaScript questions that test implicit coercion, explicit casts, string and number conversions, truthy/falsy evaluations, equality quirks, arithmetic side effects, ToPrimitive algorithms, JSON behavior, and the most common pitfalls developers hit when the engine reshapes data types.

12

Basic Error Types (SyntaxError, TypeError)

40

Explore 40 JavaScript questions covering SyntaxError definitions, parsing mistakes, prevention strategies, TypeError causes, undefined versus null access issues, strict mode implications, debugging stacks, try/catch usage, and best practices for runtime resilience.

13

Console API (log, error, table)

40

Explore 40 questions that cover console.log, console.error, console.table, message formatting, styling, grouping, timing, assertions, debugging workflows, clearing output, and practical logging best practices in JavaScript.

14

Basic Debugging in Browser DevTools

30

Understand 30 questions covering how to open DevTools, inspect the DOM, use the console, set and manage breakpoints, step through code, inspect the call stack, monitor network calls, leverage overrides, analyze performance and memory, debug event listeners, and work in responsive design mode.

15

Math Object & Random Numbers

50

Explore 50 JavaScript questions covering Math constants, rounding methods, min/max, exponentiation, roots, absolute values, sign detection, trig/log functions, random generation, range helpers, conceptual seeding, randomization patterns, and performance tips for numerical code.

16

Array Iteration Essentials (forEach)

40

Cover 40 questions on how Array.forEach works, callback parameters, side effects, mutation patterns, differences versus loops and map/filter, thisArg usage, arrow callbacks, early-exit limitations, nested iterations, object handling, common patterns, debugging techniques, and best practices.

17

Basic Date Handling (Date object)

50

Answer 50 questions on JavaScript Date basics: creating instances, timestamps, extracting components, setting values, parsing strings, basic formatting, Date.now, arithmetic, time zones, UTC helpers, comparisons, ISO conversion, and common pitfalls.

18

Intro to DOM (querySelector & textContent)

40

Answer 40 questions covering DOM fundamentals, document structure, element selection with querySelector/querySelectorAll, CSS selector usage, reading and updating textContent, handling null results, safe DOM manipulation, and best practices.

19

Prototype & Inheritance

75

Tackle 75 questions covering prototype chain fundamentals, __proto__ vs prototype, constructor functions, adding and overriding prototype methods, Object.create patterns, class syntax with extends/super, distinguishing instance vs prototype data, checking inheritance relationships, understanding this, performance considerations, pitfalls, and best practices.

20

Classes & OOP

50

Work through 50 questions on class syntax, constructors, instance and static members, getters/setters, inheritance with extends/super, private fields, composition vs inheritance, using this, creating multiple instances, basic design patterns, and best practices.

21

Modules (import/export)

50

Answer 50 questions on ES modules: named vs default exports, import syntax variations, renaming, exporting functions/classes/constants, re-exporting, module scope, namespace imports, dynamic import(), browser/module loading, resolution rules, Node.js ESM/CommonJS, bundling basics, and best practices.

22

Error Handling (try, catch, finally)

40

Tackle 40 questions on why try/catch exists, how to structure catch/finally blocks, inspecting error objects, throwing custom errors, handling specific cases, nesting handlers, and modern best practices.

23

Asynchronous JS (Callbacks)

75

Answer 75 questions on asynchronous JavaScript callbacks: fundamentals, error-first patterns, execution order, callback hell, timers, DOM and I/O callbacks, higher-order functions, data passing, chaining, and modern replacements like Promises.

24

Promises & Promise Chaining

40

Tackle 40 questions about JavaScript Promises: states, creating promises, then/catch/finally, value chaining, error propagation, avoiding callback hell, Promise.all, Promise.race, and coordinating multiple async operations.

25

Async/Await Deep Understanding

40

Answer 40 questions on async/await internals: how async functions work, await behavior, try/catch error handling, sequential vs parallel flows, awaiting multiple promises, mixing with raw promises, event loop interaction, return values, pitfalls, and best practices.

26

Execution Context

40

Dive into 40 questions covering how JavaScript builds global and function execution contexts, creation and execution phases, lexical and variable environments, scope chains, hoisting, this binding, and call stack behavior.

27

Hoisting & Temporal Dead Zone

40

Tackle 40 questions covering hoisting concepts, var behavior, function declaration hoisting, function expressions, let/const characteristics, temporal dead zone pitfalls, runtime errors, and best practices.

28

Closures & Lexical Environment

40

Study 40 JavaScript questions on lexical scoping, scope chains, closure creation, accessing outer variables, state preservation, memory considerations, and avoiding accidental closures.

29

Scope Types (Global, Block, Function)

30

Learn 30 questions that analyze JavaScript global scope, function scope, block scope, var quirks, visibility rules, shadowing, scope chains, and best practices for managing identifiers.

30

Event Loop & Microtasks Introduction

50

Answer 50 questions about the JavaScript event loop, call stack, macrotasks, microtasks, promise timing, rendering, async APIs, starvation risks, and debugging workflows.

31

Advanced Array Methods (map, filter, reduce)

35

Answer 35 questions that dive into map transformations, filter logic, reduce accumulations, callback signatures, immutability, chaining, patterns, performance trade-offs, and behavior comparisons.

32

Spread & Rest Operator Deep Usage

35

Answer 35 questions exploring spread on arrays and objects, cloning behavior, combining collections, rest parameters, destructuring techniques, pitfalls, performance trade-offs, and modern practical patterns.

33

6 Destructuring Use Cases (Nested, Default)

30

Tackle 30 questions on nested object/array destructuring, defaults, renaming bindings, destructuring parameters, and skipping positions.

34

Template Literals Advanced (Tagged Templates)

35

Answer 35 questions digging into template literal basics, tagged function mechanics, string/value processing, security sanitization, custom formatting, localization, DSL construction, and performance trade-offs.

35

Regular Expressions Basics

35

Answer 35 questions covering regex literal vs constructor syntax, metacharacters, character classes, quantifiers, anchors, grouping, escaping, and JS testing/matching methods.

36

Shallow vs Deep Copying Objects

30

Answer 30 questions comparing shallow copy techniques, deep copy strategies, spread/Object.assign behavior, JSON and structuredClone approaches, reference vs value semantics, and common pitfalls like cyclic structures.

37

JSON Handling (stringify, parse pitfalls)

40

Answer 40 questions covering JSON.stringify basics, JSON.parse behavior, handling undefined and functions, circular structure errors, Date serialization, number precision, reviver/replacer usage, and safe parsing practices.

38

DOM Events Bubbling & Capturing

30

Answer 30 questions on event propagation phases, capturing basics, target behavior, bubbling mechanics, addEventListener options, stopping propagation, preventing default actions, and event delegation techniques.

39

Performance Optimization Techniques

35

Answer 35 questions on minimizing reflows, debouncing/throttling, faster loops, efficient structures, avoiding leaks, web workers, lazy loading, caching, cutting re-renders, and profiling with DevTools.

40

Iterators & Generators (yield, next, custom iterators)

35

Answer 35 questions covering iterator protocol basics, next() behavior, iterable objects, generator syntax, yield mechanics, execution control, passing values, custom iterators, lazy generator use cases, and async-iterator differences.

41

Async Iteration & for-await-of

35

Answer 35 questions covering the async iterator protocol, Symbol.asyncIterator, async generator syntax, yield vs yield*, promise handling, for-await-of mechanics, error management, streaming data scenarios, and using async generators with fetch.

42

Debounce & Throttle Patterns

35

Answer 35 questions covering debounce timing, throttle intervals, leading/trailing triggers, preventing noisy events, scroll/input use cases, manual implementations, pitfalls, and UI performance gains.

43

Shadow DOM & Web Components Basics

35

Answer 35 questions on custom element fundamentals, shadow DOM encapsulation, open vs closed roots, templates and slots, style isolation, lifecycle callbacks, reusable component design, and light/shadow DOM interaction.

44

Intersection Observer

35

Answer 35 questions covering observers and targets, threshold/rootMargin tuning, lazy-loading patterns, visibility detection, cleanup best practices, entry properties, performance wins vs scroll events, and common use cases like infinite scroll, animations, and analytics.

45

MutationObserver: Watching DOM Changes

35

Test your knowledge with 35 questions on MutationObserver—covering DOM observation, configuration options, attribute and child tracking, subtree monitoring, mutation records, cleanup, performance, and real-world use cases.

46

Browser Rendering Pipeline

35

Test your understanding of how browsers render web pages with 35 questions covering HTML/CSS/JS parsing, the Critical Rendering Path, layout, painting, compositing, and performance optimizations.

47

Security Basics

40

Test your knowledge with 40 questions on web security fundamentals—covering XSS types, prevention strategies, CSRF mechanics, and defense techniques like tokens, SameSite cookies, and Content Security Policy.