BudiBaduQuiziBadu

JavaScript Intro to DOM (querySelector & textContent) Quiz

JavaScript
0 Passed
0% acceptance

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.

40 Questions
~80 minutes
1

Question 1

What is the DOM?

A
A tree-like representation of the HTML document accessible via JavaScript
B
A CSS preprocessor
C
A database schema
D
A file system
2

Question 2

What does the document root node typically represent in browsers?

A
<html>
B
<body>
C
<head>
D
window
3

Question 3

Which property references the top-level document object?

A
window.document
B
document.window
C
global.documentRoot
D
dom
4

Question 4

What does document.body return?

A
The <body> element
B
All elements
C
A NodeList of children
D
null in fully loaded pages
5

Question 5

How are DOM nodes related to each other?

A
Through parent-child and sibling relationships forming a tree
B
In a flat array
C
Only parent references exist
D
Nodes are unrelated
6

Question 6

Which method finds the first matching element by CSS selector?

A
document.querySelector(selector)
B
document.getElementById(selector)
C
document.selectFirst(selector)
D
document.query(selector)
7

Question 7

What does document.querySelectorAll(".item") return?

A
A static NodeList of all elements with class item
B
A live HTMLCollection
C
An array
D
Only the first match
8

Question 8

Which CSS selector targets an element by ID?

A
#header
B
.header
C
header
D
*header
9

Question 9

What does this code log?

javascript
const title = document.querySelector('h1')
console.log(title)
console.log(title ? title.textContent : 'missing')
A
The h1 element reference and its text content if found
B
Always null
C
Throws if no h1 exists
D
Logs NodeList
10

Question 10

How do you iterate over querySelectorAll results?

javascript
const items = document.querySelectorAll('.item')
items.forEach(node => console.log(node.textContent))
A
NodeList has forEach in modern browsers to loop elements
B
NodeList must be converted to array first
C
forEach throws on NodeList
D
textContent is unavailable
11

Question 11

Which code handles missing elements gracefully?

javascript
const subtitle = document.querySelector('.subtitle')
if (subtitle) {
  console.log(subtitle.textContent)
}
A
Checks for null before accessing textContent to avoid errors
B
Throws due to if statement
C
subtitle always exists
D
textContent returns null
12

Question 12

What does this CSS selector match?

A
.card > .title selects .title elements that are direct children of .card
B
.card .title selects only direct children
C
.card + .title selects nested titles
D
.card.title selects two tags
13

Question 13

How do you select the element with attribute data-role="dialog"?

A
document.querySelector('[data-role="dialog"]')
B
document.querySelector('data-role=dialog')
C
document.querySelector('#data-role="dialog"')
D
document.getElementByDataRole("dialog")
14

Question 14

What does querySelectorAll return when no matches exist?

A
An empty NodeList
B
null
C
Throws ReferenceError
D
Undefined
15

Question 15

What is the difference between textContent and innerText?

A
textContent returns all text nodes regardless of CSS, innerText respects layout and CSS visibility
B
innerText is faster and standard
C
textContent strips whitespace differently
D
They are identical
16

Question 16

Which property updates an element’s textual content without parsing HTML?

javascript
const message = document.querySelector('#message')
message.textContent = 'Updated!'
A
textContent replaces the text contents safely
B
innerHTML
C
innerText always
D
nodeValue on the element
17

Question 17

How do you append additional text using textContent?

javascript
const statusEl = document.querySelector('.status')
statusEl.textContent += ' - Complete'
A
Concatenates strings; text nodes are updated entirely
B
Appends DOM nodes automatically
C
Throws TypeError
D
Requires innerHTML
18

Question 18

What does element.textContent = "" do?

A
Clears all text nodes inside the element
B
Removes the element
C
Throws error
D
Only hides text visually
19

Question 19

How do you safely update text on an element that might be null?

javascript
const alertBox = document.querySelector('.alert')
if (alertBox) {
  alertBox.textContent = 'Saved!'
}
A
Check for null before assignment to avoid runtime errors
B
textContent handles null automatically
C
Use alertBox.innerText only
D
Replace .alert with querySelectorAll
20

Question 20

Which scenario favors textContent over innerHTML?

A
Rendering user-generated text to avoid HTML injection
B
Inserting markup with tags
C
Adding event listeners
D
Changing classes
21

Question 21

What does this code output when the element has nested spans?

xml
<p id="info">Hello <span>World</span></p>
const el = document.querySelector('#info')
console.log(el.textContent)
A
Hello World
B
Hello
C
Only the span text
D
null
22

Question 22

How do you select the first <li> inside a .nav list?

javascript
const firstItem = document.querySelector('.nav li')
A
Combining selectors selects the first matching descendant li
B
Requires .nav > li
C
Cannot select li via querySelector
D
Returns NodeList
23

Question 23

What is a common pattern for caching DOM references?

A
Store query results in const variables to reuse them instead of querying repeatedly
B
Query inside every click handler without caching
C
Use global querySelector always
D
Only use IDs and no classes
24

Question 24

Why should you store NodeList results before manipulating them?

A
To iterate multiple times without re-querying and to avoid stale references
B
NodeLists mutate automatically
C
Required by browsers
D
NodeLists are arrays
25

Question 25

What is printed here?

javascript
const nodes = document.querySelectorAll('.item')
for (const node of nodes) {
  console.log(node.textContent.trim())
}
A
Each .item text, trimmed, logged in order
B
Throws because NodeList is not iterable
C
Only first item
D
Whitespace only
26

Question 26

Which code updates multiple elements with the same text?

javascript
document.querySelectorAll('.price').forEach(node => {
  node.textContent = '$9.99'
})
A
Sets textContent on every matched .price element
B
Only updates the first one
C
Requires innerHTML
D
Throws due to NodeList
27

Question 27

How do you ensure an element exists before using it in multiple functions?

A
Query once, store in const el, check el before passing around
B
Query repeatedly without checking
C
Wrap code in try/catch always
D
Use innerHTML
28

Question 28

Which code snippet demonstrates reading textContent safely with optional chaining?

javascript
const subtitleText = document.querySelector('.subtitle')?.textContent || ''
A
Returns textContent or empty string if element is null
B
Throws if element missing
C
Optional chaining unsupported
D
textContent is undefined always
29

Question 29

Why should you avoid direct innerHTML assignments when only text needs updating?

A
innerHTML parses HTML and is slower; textContent is safer and faster for plain text
B
innerHTML is deprecated
C
textContent doesn’t work
D
innerHTML doesn’t exist
30

Question 30

What is a safe approach when manipulating user-generated text?

A
Insert it via textContent to prevent user HTML from executing
B
Use innerHTML so formatting is preserved
C
Use eval on text
D
Use document.write
31

Question 31

How do you avoid layout thrashing when updating multiple elements?

A
Batch DOM reads and writes; modify elements together before forcing reflow
B
Force layout after every change
C
Use alert between updates
D
Query after each write
32

Question 32

Which pattern avoids repeated DOM queries inside loops?

A
const list = document.querySelector(".list"); forEach use list
B
Call document.querySelector repeatedly inside the loop
C
Use global selectors each time
D
Use innerHTML instead
33

Question 33

What is printed if querySelector finds no match?

javascript
const node = document.querySelector('.missing')
console.log(node)
A
null
B
undefined
C
Throws error
D
Empty NodeList
34

Question 34

How do you convert a NodeList to an array?

A
Array.from(document.querySelectorAll(".item"))
B
[...document.querySelector(".item")]
C
NodeList.toArray()
D
JSON.parse(NodeList)
35

Question 35

Which strategy prevents errors when manipulating optional elements?

A
Guard each query result or use optional chaining before calling properties
B
Assume elements exist
C
Wrap in try/catch always
D
Use innerHTML
36

Question 36

Why is storing DOM references in module scope useful?

A
It avoids repeated queries when the same element is needed in multiple functions
B
It prevents garbage collection
C
It hides elements automatically
D
It disables reflow
37

Question 37

What does document.querySelector("div.highlight span") select?

A
First span descendant inside a div with class highlight
B
All spans globally
C
Only direct child span
D
All highlighted elements
38

Question 38

Why might you store query results in const instead of let?

A
DOM references rarely need reassignment; const documents intent
B
const makes NodeList immutable
C
const is required
D
let is slower
39

Question 39

What best describes the DOM rendering flow regarding textContent updates?

A
Updating textContent schedules reflow/repaint; batch updates to minimize layout passes
B
textContent bypasses rendering
C
textContent updates require reload
D
textContent changes only on DOMContentLoaded
40

Question 40

What is a recommended best practice for DOM manipulation?

A
Use precise selectors, cache references, guard against null, and update text via textContent when HTML is not needed
B
Use innerHTML for all updates
C
Assume elements exist and skip checks
D
Store NodeList in global variables always

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.