JavaScript Notes
HubYour First JavaScript Program — Hello World & Beyond Complete Guide 2026History of JavaScript — Complete Timeline from 1995 to 2026How JavaScript Runs — Complete Guide to Execution, Call Stack & Event LoopJavaScript Engine Explained — V8, JIT Compilation & How Code Gets FastJavaScript Use Cases — 15 Things You Can Build with JavaScript (2026)JavaScript vs Other Languages — Complete Comparison Guide 2026What is JavaScript? Complete BeginnerWhy Learn JavaScript in 2026? Career, Salary, Scope & Benefits GuideJavaScript Break Statement Tutorial – Complete Guide with ExamplesJavaScript Break and Continue Statements – Complete Guide with ExamplesJavaScript Continue Statement Tutorial – Skip Iterations with ExamplesJavaScript Do While Loop Tutorial – Execute at Least Once with ExamplesJavaScript Do-While Loop Tutorial – Complete Guide with ExamplesJavaScript For Loop Tutorial – Complete Guide with ExamplesJavaScript If Statement Tutorial – Conditional Logic with ExamplesJavaScript If Else Statement Tutorial – Complete Guide with ExamplesJavaScript If Statement Tutorial – Complete Guide with ExamplesJavaScript Nested If Statement Tutorial – Multi-Level Conditions with ExamplesNested Loops in JavaScriptJavaScript Control Flow Practice Programs – 20+ Exercises with SolutionsJavaScript Switch Statement Tutorial – Case Matching with ExamplesSwitch Statement in JavaScriptJavaScript While Loop Tutorial – Complete Guide with ExamplesJavaScript Arrow Functions Tutorial – Syntax, Use Cases & this BindingJavaScript Callback Functions Explained – Synchronous & AsynchronousJavaScript Closures Explained – Lexical Scope, Private State & MemoryJavaScript Function Declaration Tutorial – Hoisting, Syntax & ScopeJavaScript Function Expression Tutorial – Anonymous, Named & AssignedJavaScript Higher Order Functions Tutorial – map, filter, reduce & Custom HOFsJavaScript IIFE Explained – Immediately Invoked Function ExpressionJavaScript Functions Practice Programs – 20+ Exercises with SolutionsJavaScript Recursion Tutorial – Call Stack, Base Case & Recursive PatternsJavaScript Array Basics - Complete BeginnerJavaScript Array Methods - Complete Reference Guide with ExamplesJavaScript Array Programs - 20+ Practice Problems with SolutionsJavaScript Arrays Basics - Complete Guide with Examples & DiagramsJavaScript Array filter() Method - Complete Tutorial with ExamplesJavaScript filter() Method — Complete Guide with Examples 2026JavaScript Array find() Method - Complete Tutorial with ExamplesJavaScript find() & findIndex() — Complete Guide 2026JavaScript Array map() Method - Complete Tutorial with ExamplesJavaScript map() Method — Transform Arrays Complete Guide 2026JavaScript map() vs forEach() - Key Differences with ExamplesJavaScript Array push() and pop() - Complete Tutorial with ExamplesJavaScript Array reduce() Method - Complete Tutorial with ExamplesJavaScript reduce() Method — Complete Deep Dive with Examples 2026JavaScript Array shift() and unshift() - Complete Tutorial with ExamplesJavaScript Array sort() Method - Complete Tutorial with ExamplesJavaScript splice() vs slice() - Complete Tutorial with ExamplesJavaScript Object Destructuring - Complete Guide with ExamplesJavaScript Objects - Complete Guide to Object Basics with ExamplesJavaScript Object Methods - Built-in Methods & Custom Methods Complete GuideJavaScript Object Programs - Practice Problems with SolutionsJavaScript Object Properties - Keys, Values, Descriptors & Dynamic PropertiesJavaScript Rest Operator (...) - Parameters, Destructuring & Complete GuideJavaScript Spread Operator (...) - Complete Guide with ExamplesJavaScript this Keyword - Complete Guide with Binding Rules & ExamplesJavaScript String Basics - Complete Guide to Strings with ExamplesJavaScript String Methods - Complete Reference with Examples & OutputJavaScript String Programs - Practice Problems with SolutionsJavaScript String Replacing - replace(), replaceAll() & Regex Patterns GuideJavaScript String Searching Methods - includes, indexOf, startsWith, match GuideJavaScript Template Literals (ES6) - Complete Guide with Tagged TemplatesJavaScript DOM Changing Content - textContent, innerHTML, setAttribute Complete GuideJavaScript DOM Changing Styles - CSS Manipulation, classList & getComputedStyleJavaScript DOM Creating Elements - createElement, appendChild, DocumentFragment GuideJavaScript DOM Introduction - Complete Guide to Document Object ModelJavaScript DOM Traversal - Navigate Parent, Child & Sibling NodesJavaScript DOM Forms - Form Handling, Validation & FormData Complete GuideJavaScript localStorage - Complete Guide to Web Storage APIlocalStorage vs sessionStorage - JavaScript Web Storage Comparison GuideJavaScript DOM Removing Elements - remove(), removeChild() Complete GuideJavaScript DOM Selecting Elements - querySelector, getElementById Complete GuideJavaScript sessionStorage - Complete Guide to Session-Based Web StorageJavaScript Click Event - addEventListener, Event Handler Complete GuideEvent Bubbling in JavaScript – Complete Guide with Examples (2026)Event Capturing in JavaScript – Complete Guide to Capture Phase (2026)Event Delegation in JavaScript – Complete Guide with Examples (2026)JavaScript Event Object – Complete Guide with Examples (2026)JavaScript Form Events – Complete Guide with Examples (2026)JavaScript Keyboard Events – Complete Guide to keydown, keyup & Key Properties (2026)JavaScript Mouse Events – Complete Guide with Examples (2026)JavaScript Async Await - Complete Guide with Examples & Error HandlingJavaScript Call Stack - Complete Guide with Visual Diagrams & ExamplesJavaScript Callback Queue (Task Queue) - Complete Guide with DiagramsJavaScript Callbacks - Complete Guide with Callback Hell & PatternsJavaScript Event Loop - Complete Guide with Visual Diagrams & ExamplesJavaScript Fetch API - Complete Guide with Examples, Error Handling & Async/AwaitJSON in JavaScript - Complete Guide: Parse, Stringify, Fetch & Error HandlingJavaScript Promise.all, Promise.race, Promise.any, Promise.allSettled — Complete Guide 2026JavaScript Promises - Complete Guide with Chaining, Error Handling & Event LoopSynchronous vs Asynchronous JavaScript — Complete Explanation 2026JavaScript Web APIs - Complete Guide: setTimeout, fetch, DOM Events & MoreClosures in JavaScript — Complete Guide with Examples 2026Hoisting in JavaScript — Complete Guide with Examples 2026Prototype in JavaScript — Complete Guide with Examples 2026Scope in JavaScript — Complete Guide with Examples 2026Browser Object Model (BOM) in JavaScript — Complete GuideCanvas API in JavaScript — Complete Drawing & Animation GuideDrag and Drop API in JavaScript — Complete TutorialGeolocation API in JavaScript — Get User Location TutorialHistory API in JavaScript — SPA Routing & pushState GuideNotification API in JavaScript — Push Notifications TutorialService Workers in JavaScript — Offline, Caching & PWA GuideWeb Storage API in JavaScript — localStorage & sessionStorage GuideWeb Workers in JavaScript — Multithreading & Background Tasks GuideJavaScript Interview — Behavioral Questions and Soft Skills Guide 2026Common JavaScript Interview Mistakes — What to Avoid 2026JavaScript Interview Tips — Strategy and Preparation Guide 2026JavaScript Mock Interview — Practice Questions with Solutions 2026JavaScript System Design — Frontend Architecture Interview Guide 2026JavaScript apply() Method - Complete Guide with ExamplesJavaScript bind() Method - Complete Guide with ExamplesJavaScript call() Method - Complete Guide with ExamplesJavaScript call() vs apply() vs bind() - Complete Comparison GuideJavaScript Currying - Complete Guide with ExamplesJavaScript Debounce - Complete Guide with Timeline DiagramsJavaScript Execution Context - Complete Guide with Stack DiagramsJavaScript Garbage Collection - Memory Lifecycle & Mark-and-Sweep GuideJavaScript Generators - Complete Guide with yield and IterationJavaScript Hoisting - Complete Guide with var, let, const & FunctionsJavaScript Iterators - Complete Guide with Iterator ProtocolJavaScript Lexical Scope - Complete Guide with Scope Chain DiagramsJavaScript Memory Management - Complete Guide with Lifecycle DiagramsJavaScript Modules - Complete Guide with import export ExamplesJavaScript Scope - Complete Guide with var, let, const & Scope ChainJavaScript Symbols - Complete Guide with Well-Known SymbolsJavaScript Throttle - Complete Guide with Timeline DiagramsJavaScript Comments Complete Guide – Single Line, Multi-line & JSDoc with ExamplesJavaScript Data Types Complete Guide – Primitives, Objects & typeof with ExamplesJavaScript Input and Output Complete Guide – console.log, prompt, alert & DOM with ExamplesJavaScript Keywords Complete Guide – Reserved Words List with Examples for BeginnersJavaScript null vs undefined – Complete Guide with Differences, Examples & Interview Q&AJavaScript Operators Complete Guide – Arithmetic, Comparison, Logical & More with ExamplesJavaScript Strict Mode Complete Guide – JavaScript Type Conversion Complete Guide – Explicit & Implicit Coercion with ExamplesJavaScript var vs let vs const – Complete Guide with Scope, Hoisting & Best PracticesJavaScript Variables Complete Guide – Declaration, Naming Rules & Memory Model for BeginnersDeque (Double-Ended Queue) in JavaScript — Complete GuideLinked List in JavaScript — Nodes, Pointers & Operations GuideJavaScript Map — Key-Value Data Structure Complete GuideJavaScript Numbers — IEEE 754, Precision, and Number Methods GuidePriority Queue in JavaScript — Min Heap Implementation GuideQueue Data Structure in JavaScript — FIFO, Enqueue & Dequeue ExplainedJavaScript Set — Unique Values Data Structure GuideSorting Algorithms in JavaScript — Bubble, Merge, Quick Sort GuideStack Data Structure in JavaScript — LIFO, Push, Pop ExplainedJavaScript Typed Arrays — ArrayBuffer, Int32Array, Float64Array GuideJavaScript WeakMap — Weak References, Memory Management GuideJavaScript WeakSet — Complete Guide with Examples 2026Applications of JavaScript — Where JS is Used in 2026 Complete GuideJavaScript Backend Frameworks — Node.js, Express, NestJS Complete Guide 2026JavaScript Frontend Libraries — React, Vue, Angular, Svelte Complete Overview 2026JavaScript Full-Stack Frameworks — Next.js, Remix, Astro Complete Guide 2026JavaScript Career Paths & Jobs — Salary, Roles & Roadmap 2026JavaScript Libraries vs Frameworks — Difference & Examples Complete Guide 2026JavaScript Custom Errors – Extend Error Class, Custom Error Types & instanceofJavaScript Debugging – console Methods, DevTools, Breakpoints & Error Stack TracesJavaScript throw Statement – Throw Errors, Custom Messages & Error TypesJavaScript Try Catch Finally – Error Handling Complete GuideTop 30 JavaScript Closure Interview Questions & Answers 2026Top 30 JavaScript Coding Interview Questions 2026 (With Solutions)Top 25 JavaScript Event Loop Interview Questions & Answers 2026Top 50 JavaScript Interview Questions & Answers 2026Top 30 JavaScript Promise Interview Questions & Answers 202650 Tricky JavaScript Output Questions 2026 (With Answers)Build a JavaScript Calculator - Step by Step Project TutorialBuild a JavaScript Image Carousel - Step by Step Project TutorialBuild a JavaScript Counter Application - Step by Step Project TutorialBuild a JavaScript Digital Clock - Step by Step Project TutorialBuild a Dynamic Resume Builder in JavaScript - Step by Step TutorialBuild a JavaScript Email Validator - Step by Step Project TutorialBuild a JavaScript Employee Database Management App - Step by Step TutorialBuild a JavaScript Expense Tracker - Step by Step Project TutorialBuild a GitHub Profile Search App in JavaScript - Step by Step TutorialBuild a JavaScript Image Slider - Step by Step Project TutorialBuild a JavaScript Multi-Step Progress Bar - Step by Step TutorialBuild JavaScript Nested Chat Comments - Step by Step Project TutorialBuild a JavaScript Notes App - Step by Step Project TutorialBuild a JavaScript OTP Input Field - Step by Step Project TutorialBuild a JavaScript Palindrome Checker - Step by Step Project TutorialBuild a JavaScript Price Range Slider - Step by Step Project TutorialBuild a JavaScript Prime Number Checker - Step by Step Project TutorialBuild a JavaScript QR Code Generator - Step by Step Project TutorialBuild a JavaScript QR Code Scanner - Step by Step Project TutorialBuild a JavaScript Quiz App - Step by Step Project TutorialBuild a JavaScript Random Number Generator - Step by Step TutorialBuild a JavaScript Random Password Generator - Step by Step TutorialJavaScript Image Resize & Compress — Canvas API Project 2026JavaScript Responsive Admin Dashboard — DOM & CSS Project 2026JavaScript Show/Hide Password Toggle — Beginner DOM Project 2026JavaScript Sortable Filterable Table — DOM & Array Methods Project 2026JavaScript Stopwatch Project — setInterval & DOM Tutorial 2026JavaScript Student Grade Calculator — Arrays & Logic Project 2026JavaScript Task Scheduler Project — CRUD & localStorage Tutorial 2026JavaScript Tic-Tac-Toe Game — DOM Manipulation Project Tutorial 2026JavaScript Toast Notification Project — Custom Alerts Tutorial 2026Build a Todo App in JavaScript - Step by Step Project TutorialJavaScript Unicode Character Value Finder — charCodeAt & fromCharCode Project 2026JavaScript Weather App Project — Fetch API & DOM Complete Tutorial 2026JavaScript Cheat Sheet 2026 — Complete Quick ReferenceImportant JavaScript Concepts Every Developer Must Know in 2026JavaScript One Shot Notes 2026 — Complete JS in One PageJavaScript Quick Revision Notes — Interview Prep in 30 Minutes 2026Abstraction in JavaScript OOP – Hide Complexity, Expose SimplicityJavaScript Classes Tutorial – ES6 Class Syntax, Inheritance & MoreJavaScript Constructor Functions – new Keyword, Prototype & OOP PatternsEncapsulation in JavaScript – Private Fields, Getters, Setters & Data ProtectionJavaScript Inheritance – extends, super, and Prototype-Based InheritanceObject-Oriented Programming in JavaScript – OOP Concepts Complete GuideJavaScript OOP Projects – Build Real-World Apps with Classes & OOPPolymorphism in JavaScript – Method Overriding, Duck Typing & Many FormsJavaScript Prototype Chain – How Property Lookup Works in JavaScriptJavaScript Prototypes – Prototype-Based Inheritance, Object.create & prototype PropertyJavaScript Advanced Practice Problems — 15+ Interview-Level Challenges 2026JavaScript Assignments — 10 Project-Based Learning Tasks 2026JavaScript Beginner Practice Problems — 20+ Coding Exercises 2026JavaScript Coding Challenges — 25 Interview-Style Problems 2026JavaScript Intermediate Practice Problems — 20+ Coding Challenges 2026JavaScript MCQs — 50 Multiple Choice Questions with Answers 2026JavaScript Regex Character Classes – [abc], [^abc], Ranges & ShortcutsJavaScript Regex Email Validation – Pattern, Edge Cases & Best PracticesJavaScript Regex Flags – g, i, m, s, u, y Flags Explained with ExamplesJavaScript Regex Groups – Capturing, Non-Capturing & Named GroupsJavaScript Number Validation with Regex — Complete Patterns & Examples 2026JavaScript Password Validation with Regex — Strength Checker & Patterns 2026JavaScript Regex Quantifiers – *, +, ?, {n,m}, Greedy vs Lazy MatchingJavaScript Regex Basics – Regular Expressions Tutorial for BeginnersJavaScript Regex Projects — 10 Practical Mini-Projects with Code 2026JavaScript URL Validation with Regex — Complete Patterns & Examples 2026JavaScript Username Validation with Regex — Patterns & Form Examples 2026JavaScript TutorialJavaScript Lazy Loading — Images, Modules & Components Complete Guide 2026JavaScript Performance Optimization — Speed Up Your Code Complete Guide 2026JavaScript Unit Testing with Jest — Complete Guide for Beginners 2026
Master JavaScript regex quantifiers: *, +, ?, {n}, {n,m}, greedy vs lazy matching, possessive, and real-world examples for form validation patterns. Interview Q&A included.
Quantifiers specify how many times a character, group, or character class must appear for the pattern to match. They are the key to matching variable-length text like phone numbers, passwords, and usernames.
📊 Quantifiers Visual Reference
Example
QUANTIFIER │ MEANING │ EXAMPLE │ MATCHES
────────────┼───────────────────────┼────────────┼──────────────────
* │ 0 or more │ /ab*/ │ "a", "ab", "abb"
+ │ 1 or more │ /ab+/ │ "ab", "abb" (not "a")
? │ 0 or 1 (optional) │ /colou?r/ │ "color", "colour"
{n} │ exactly n times │ /\d{4}/ │ "2026" (exactly 4)
{n,} │ n or more │ /\d{2,}/ │ "12", "123", "1234"
{n,m} │ between n and m │ /\d{2,4}/ │ "12", "123", "1234"
GREEDY vs LAZY:
* → greedy (matches as MUCH as possible)
*? → lazy (matches as LITTLE as possible)
+ → greedy
+? → lazy
? → greedy
?? → lazy
💻 Example 1 — Basic Quantifiers
js example
// * — zero or more
console.log(/ab*/.test("a")); // true — 'b' appears 0 times
console.log(/ab*/.test("ab")); // true — 'b' appears 1 time
console.log(/ab*/.test("abbb")); // true — 'b' appears 3 times
console.log(/ab*/.test("cd")); // false — no 'a' at all
// + — one or more
console.log(/ab+/.test("a")); // false — 'b' must appear at least once
console.log(/ab+/.test("ab")); // true
console.log(/ab+/.test("abbb")); // true
// ? — zero or one (optional)
console.log(/colou?r/.test("color")); // true — 'u' is optional
console.log(/colou?r/.test("colour")); // true — 'u' is present
console.log(/colou?r/.test("colouur")); // false — 'uu' is not {0,1}Output
true true true false false true true true true false
💻 Example 2 — Exact and Range Quantifiers {n}, {n,m}
Example
// {n} — exactly n times
console.log(/^\d{4}$/.test("2026")); // true — exactly 4 digits
console.log(/^\d{4}$/.test("20")); // false — only 2 digits
console.log(/^\d{4}$/.test("20268")); // false — 5 digits
// {n,} — n or more
console.log(/^\d{3,}$/.test("123")); // true — 3 or more digits
console.log(/^\d{3,}$/.test("1234567")); // true
console.log(/^\d{3,}$/.test("12")); // false — only 2
// {n,m} — between n and m
const usernamePattern = /^[a-zA-Z0-9_]{3,16}$/;
console.log(usernamePattern.test("riya")); // true — 4 chars
console.log(usernamePattern.test("r")); // false — too short
console.log(usernamePattern.test("a".repeat(17))); // false — too long
console.log(usernamePattern.test("Riya_123")); // true — 8 chars
Output
true false false true true false true false false true
💻 Example 3 — Greedy vs Lazy Matching
Example
const html = "<b>bold</b> and <i>italic</i>";
// Greedy — matches as MUCH as possible (default)
const greedy = html.match(/<.+>/);
console.log("Greedy:", greedy[0]);
// Lazy — matches as LITTLE as possible (add ? after quantifier)
const lazy = html.match(/<.+?>/g);
console.log("Lazy:", lazy);
// Another example: extract quoted strings
const text = '"first" and "second" and "third"';
const greedyQuotes = text.match(/".*"/); // greedy: matches from first to LAST "
console.log("Greedy quotes:", greedyQuotes[0]);
const lazyQuotes = text.match(/".*?"/g); // lazy: each shortest match
console.log("Lazy quotes:", lazyQuotes);
Output
Greedy: <b>bold</b> and <i>italic</i> Lazy: [ '<b>', '</b>', '<i>', '</i>' ] Greedy quotes: "first" and "second" and "third" Lazy quotes: [ '"first"', '"second"', '"third"' ]
💻 Example 4 — Practical Validation Patterns
Example
// Indian phone: 10 digits starting with 6-9
const phone = /^[6-9]\d{9}$/;
console.log(phone.test("9876543210")); // true
console.log(phone.test("1234567890")); // false — starts with 1
console.log(phone.test("98765432")); // false — only 8 digits
// PIN code: exactly 6 digits
const pincode = /^\d{6}$/;
console.log(pincode.test("110001")); // true
console.log(pincode.test("1100")); // false
// Password: 8-20 chars, at least 1 uppercase, 1 digit
const password = /^(?=.*[A-Z])(?=.*\d).{8,20}$/;
console.log(password.test("Secure123")); // true
console.log(password.test("weak")); // false
// Version number: 1.2.3 format
const version = /^\d+\.\d+\.\d+$/;
console.log(version.test("1.2.3")); // true
console.log(version.test("1.2")); // false — needs 3 parts
console.log(version.test("10.20.300")); // true
Output
true false false true false true false true false true
📋 Quantifier Quick Reference
| Quantifier | Meaning | Example | Matches |
|---|---|---|---|
* | 0 or more | /go*/ | "g", "go", "goo" |
+ | 1 or more | /go+/ | "go", "goo" (not "g") |
? | 0 or 1 | /go?/ | "g", "go" (not "goo") |
{3} | Exactly 3 | /\d{3}/ | "123" |
{3,} | 3 or more | /\d{3,}/ | "123", "1234" |
{3,5} | 3 to 5 | /\d{3,5}/ | "123", "12345" |
*? | Lazy 0 or more | /<.*?>/ | shortest match |
+? | Lazy 1 or more | /<.+?>/ | shortest match |
⚠️ Common Mistakes
❌ Mistake 1 — Greedy Quantifier Eating Too Much
Example
const text = "<div>Hello</div><div>World</div>";
console.log(text.match(/<div>.*<\/div>/)[0]); // greedy — too much!
console.log(text.match(/<div>.*?<\/div>/)[0]); // lazy — correct
Output
<div>Hello</div><div>World</div> <div>Hello</div>
❌ Mistake 2 — Forgetting ^ and $ with Quantifiers
js example
// Without anchors — partial match passes!
console.log(/\d{4}/.test("abc2026xyz")); // true — finds 2026 inside
console.log(/^\d{4}$/.test("abc2026xyz")); // false — requires FULL string to be 4 digitsOutput
true false
❌ Mistake 3 — {0,1} and ? Are Equivalent
js example
// These are the same:
console.log(/colou?r/.test("color")); // true
console.log(/colou{0,1}r/.test("color")); // true — same thingOutput
true true
🎯 Key Takeaways
- Quantifiers control how many times the preceding element must occur
*= 0 or more,+= 1 or more,?= 0 or 1 (optional){n}= exactly n,{n,}= at least n,{n,m}= between n and m- By default quantifiers are greedy — they match as much as possible
- Add
?after a quantifier (*?,+?,{n,m}?) to make it lazy (match as little as possible) - Always use
^and$anchors with quantifiers for full-string validation
❓ Interview Questions
Q1. What is a regex quantifier? > A quantifier specifies how many times the preceding element must appear. + means one or more, * means zero or more, ? means zero or one (optional), {n,m} means between n and m times.
Q2. What is greedy matching? > By default, quantifiers are greedy — they match as many characters as possible while still allowing the overall pattern to succeed. /<.+>/ on <b>text</b> matches the entire string, not just <b>.
Q3. What is lazy (non-greedy) matching? > Adding ? after a quantifier makes it lazy — it matches as few characters as possible. /<.+?>/ matches <b> (the shortest possible match), not the entire string.
**Q4. What is the difference between + and *?** > + requires at least one occurrence (one or more). * allows zero occurrences (zero or more). /\d+/ fails on non-digit strings; /\d*/ succeeds even on an empty string.
Q5. How do you match exactly 10 digits? > Use {10}: /^\d{10}$/ — the ^ and $ anchors ensure the entire string is exactly 10 digits.
Q6. What does ? after a quantifier do? > It converts the quantifier from greedy to lazy. .*? matches as few characters as possible. Without ?, .* matches as many as possible.
Q7. What is the difference between ? as a quantifier and ? in a group (?:...)? > As a quantifier after a character/group, ? means "optional" (0 or 1). Inside (?:...), the ?: is a non-capturing group modifier — different purpose entirely.
Q8. How would you validate a PIN code of exactly 4-6 digits? > /^\d{4,6}$/ — anchored with ^ and $ for full-string match, \d for digits, {4,6} for 4 to 6 repetitions.
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for JavaScript Regex Quantifiers – *, +, ?, {n,m}, Greedy vs Lazy Matching.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this JavaScript Master Course topic.
Search Terms
javascript-complete-guide, javascript master course, javascript, complete, guide, regex, quantifiers, javascript regex quantifiers – *, +, ?, {n,m}, greedy vs lazy matching
Related JavaScript Master Course Topics
Continue learning this concept
RegexJavaScript Regex Character Classes – [abc], [^abc], Ranges & ShortcutsMaster JavaScript regex character classes: square bracket syntax, negated classes, ranges [a-z], shorthand classes \\d \\w \\s, and real-world pattern examples with interview Q&A.RegexJavaScript Regex Email Validation – Pattern, Edge Cases & Best PracticesBuild a JavaScript regex email validator with step-by-step pattern breakdown, valid/invalid edge cases, HTML5 comparison, and real-world form validation function with interview Q&A.RegexJavaScript Regex Flags – g, i, m, s, u, y Flags Explained with ExamplesMaster all JavaScript regex flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode), y (sticky). With visual examples, common mistakes, and interview Q&A.RegexJavaScript Regex Groups – Capturing, Non-Capturing & Named GroupsMaster JavaScript regex groups: capturing groups (), non-capturing (?:), named groups (?<name>), backreferences, and extracting data from strings. With interview Q&A.RegexJavaScript Number Validation with Regex — Complete Patterns & Examples 2026Master number validation in JavaScript using regex patterns. Learn integer, decimal, phone, currency validation with real examples and outputs.RegexJavaScript Password Validation with Regex — Strength Checker & Patterns 2026Learn password validation regex in JavaScript. Build strength checker, validate patterns with lookaheads, and create real-time password validators.