General JavaScript Questions

In this section, we cover everything from basic to advanced JavaScript questions that you may be asked during your next phone or technical interview. We will cover the basics of JavaScript in this section, but also concentrate on the advanced topics.

Introduction - JavaScript Questions & Answers

• Basic JavaScript Questions
• Manuals & Specifications
• Code Editors
• Developer Console

JavaScript Fundamentals Q&A

• The "Script" Tag
• Code structure
• The modern mode, "use strict"
• Variables
• Data types
• Interaction: alert, prompt, confirm
• Type Conversions
• Basic operators, maths
• Comparisons
• Conditional Branching
• Logical Operators
• Nullish Coalescing Operator
• While & For Loops
• The "switch" Statement
• Functions
• Function expressions
• Arrow functions
• JavaScript Specials

Code Quality

• Debugging in the Browser
• Coding Style
• Comments
• Ninja code
• Automated testing with Mocha
• Polyfills and transpilers

Objects the Basics

• Objects
• References/Copying
• Garbage collection
• Object Methods
• The "new" Operator
• Optional Chaining
• Symbol Type
• Object to Primitive Conversion

Data Types

• Methods of Primitives
• Numbers
• Strings
• Arrays
• Array Methods
• Iterables
• Map and Set
• WeakMap and WeakSet
• Keys / Values / Entries
• Destructuring Assignment
• Date and time
• JSON Methods

Advanced Working with Functions

• Recursion & Stack
• Rest Parameters / Spread Syntax
• Variable Scope / Closures
• Var Declaration
• Global Object
• Function object / NFE
• The "new" Function Syntax
• Scheduling / Timing
• Call and Apply
• Function Binding
• Arrow Functions

Object Properties Configuration

• Property Flags / Descriptors
• Property Getters & Setters

Prototypes / Inheritance

• Prototypal Inheritance
• Function Prototypes
• Native Prototypes
• Prototype Methods

Classes

• Basic Syntax
• Class Inheritance
• Static Props / Methods
• Private, Protected Props / Methods
• Extending Built-in Classes
• Class Checking: instanceof
• Mixins

Error handling

• Error handling
• Custom Errors

Promises, Async/Await

• Callbacks
• Promises Basic
• Promises chaining
• Error / Promises
• Promise API
• Promisification
• Microtask Queue
• Async/await

Generators, Advanced Iteration

• Generators
• Async Iteration / Generators

Modules

• Modules
• Export & Import
• Dynamic imports

Miscellaneous

• Proxy and Reflect
• String Evaluation
• Currying
• Reference Type
• BigInt

Browser: Document, Events, Interfaces Questions

In this section, we will dive straight into the browser related JavaScript questions and answers that you may be asked during your next phone or technical engineering interview.

The Browser Document

• Browser Environment Specs
• DOM Tree
• Walking the DOM
• Searching the DOM
• Node Properties
• Attributes / Properties
• Modifying the Document
• Styles / Classes
• Element Size / Scrolling
• Window Sizes / Scrolling
• Coordinates

Browser Events

• Browser Events
• Bubbling / Capturing
• Event Delegation
• Browser Default Actions
• Dispatching Custom Events

UI Events

• Mouse Events
• Moving the Mouse
• Drag'n'Drop Events
• Pointer Events
• Keyboard Events
• Scrolling Events

Forms / Controls

• Form Properties / Methods
• Focusing - focus/blur
• Form Events
• Form Submit / Events

Document / Resource Loading

• Page LifeCycle
• Scripts - Async/Defer
• Resource loading

Miscellaneous

• Mutation Observer
• Selection and Range
• Event Loop

Additional Questions

In this section, we have some additional JavaScript questions and answers that may be asked during your next phone or technical engineering interview. There is no clear road map in this section, and you can choose in the order of your choosing.

Frames / Windows

• Popups / Window Methods
• Cross-Window Communication
• Clickjacking Attacks

Binary Data / Files

• ArrayBuffer, Binary Arrays
• TextDecoder / TextEncoder
• Blob Data
• File / FileReader

Network Requests

• Fetch Requests
• FormData Object
• Fetch: Download Progress
• Fetch: Abort
• Fetch: Cross-Origin Requests
• Fetch API
• URL Objects
• XMLHttpRequest
• Resumable File Upload
• Long Polling
• WebSocket
• Server Sent Events

Storing data in the browser

• Cookies, document.cookie
• LocalStorage / sessionStorage
• IndexedDB

Animation

• Bezier Curve
• CSS-Animations
• JavaScript Animations

Web Components

• Web Components
• Custom Elements
• Shadow DOM
• Template Element
• Shadow DOM Slots
• Shadow DOM Styling
• Shadow DOM / Events

Regular expressions

• Patterns and Flags
• Character Classes
• Unicode Regex
• Anchors
• Multiline Mode
• Word Boundary
• Escaping Special Characters
• Sets / Ranges
• Quantifiers
• Greedy / Lazy Quants
• Capturing Groups
• Backreferences
• Alternation
• Lookahead / Lookbehind
• Catastrophic Backtracking
• Sticky Flag
• Regex / String Methods

Bonus: Design Patterns

In this section, we have some additional questions and answers related to design patterns. Depending on the company and the interviewer. You may be asked about design patterns relative to JavaScript.

Introduction to Patterns

• What is a Pattern?
• Defining a Pattern

Creational Design Patterns

• Factory Method
• Abstract Factory
• Builder
• Constructor
• Module
• Prototype
• Singleton

Structural Design Pattern

• Adapter
• Bridge
• Composite
• Decorator
• Facade
• Flyweight
• Proxy Pattern

Behavioral Design Pattern

• Interpreter
• Template Method
• Chain of Responsibility
• Command Pattern
• Iterator
• Mediator
• Memento
• Observer Pattern
• State
• Strategy
• Visitor

Anti-Patterns