Core JavaScript Master: Prototypes, Closures, Event Loop, ES6+ & Web APIs

What is JavaScript, and what are its core architectural characteristics?

What are the primitive and reference data types in JavaScript, and how are they stored in memory?

What is the difference between JavaScript and ECMAScript?

What are the possible ways to create objects in JavaScript

What is a prototype chain

What is the Difference Between call, apply, and bind

What is JSON and its common operations

What is the purpose of the array slice method

What is the purpose of the array splice method

What is the difference between slice and splice

How do you compare Object and Map

What is the difference between == and === operators

What are lambda expressions or arrow functions

What is a first class function

What is a first order function

What is a higher order function

What is a unary function

What is the currying function

What is a pure function

What are the benefits of pure functions

What is the purpose of the let keyword

What is the difference between let and var

What is the reason to choose the name let as a keyword

How do you redeclare variables in a switch block without an error

What is the Temporal Dead Zone

What is an IIFE (Immediately Invoked Function Expression)

How do you decode or encode a URL in JavaScript?

What is memoization

What is Hoisting

What are classes in ES6

What are closures

What are modules

Why do you need modules

What is scope in javascript

What is a service worker

How do you manipulate DOM using a service worker

How do you reuse information across service worker restarts

What is IndexedDB

What is web storage

What is a post message

What is a Cookie

Why do you need a Cookie

What are the options in a cookie

How do you delete a cookie

What are the differences between cookie, local storage and session storage

What is the main difference between localStorage and sessionStorage

How do you access web storage

What are the methods available on session storage

What is a storage event and its event handler

Why do you need web storage

How do you check web storage browser support

How do you check web workers browser support

Give an example of a web worker

What are the restrictions of web workers on DOM

What is a promise

Why do you need a promise

Explain the three states of promise

What is a callback function

Why do we need callbacks

What is a callback hell

What are server-sent events

How do you receive server-sent event notifications

How do you check browser support for server-sent events

What are the events available for server sent events

What are the main rules of promise

What is callback in callback

What is promise chaining

What is promise.all

Does Promise.all() cancel the other Promises?

What is the purpose of the race method in promise

What is a strict mode in javascript

Why do you need strict mode

How do you declare strict mode

What is the purpose of double exclamation

What is the purpose of the delete operator

What is typeof operator

What is undefined property

What is null value

What is the difference between null and undefined

What is eval

What is the difference between window and document

How do you access history in javascript

How do you detect caps lock key turned on or not

What is isNaN

What are the differences between undeclared and undefined variables

What are global variables

What are the problems with global variables

What is NaN property

What is the purpose of isFinite function

What is an event flow

What is event capturing

What is event bubbling

How do you submit a form using JavaScript

How do you find operating system details

What is the difference between document load and DOMContentLoaded events

What is the difference between native, host and user objects

What are the tools or techniques used for debugging JavaScript code

What are the pros and cons of promises over callbacks

What is the difference between an attribute and a property

What is same-origin policy

What is the purpose of void 0

Is JavaScript a compiled or interpreted language

Is JavaScript a case-sensitive language

Is there any relation between Java and JavaScript

What are events

Who created javascript

What is the use of preventDefault method

What is the use of stopPropagation method

What are the steps involved in return false usage

What is BOM

What is the use of setTimeout

What is the use of setInterval

Why is JavaScript treated as Single threaded

What is an event delegation

What is ECMAScript

What is JSON

What are the syntax rules of JSON

What is the purpose JSON stringify

How do you parse JSON string

Why do you need JSON

What are PWAs

What is the purpose of clearTimeout method

What is the purpose of clearInterval method

How do you redirect new page in javascript

How do you check whether a string contains a substring

How do you validate an email in javascript

How do you get the current url with javascript

What are the various url properties of location object

How do you get query string values in javascript

How do you check if a key exists in an object

How do you loop through or enumerate javascript object

How do you test for an empty object

What is an arguments object

How do you make first letter of the string in an uppercase

What are the pros and cons of for loops

How do you display the current date in javascript

How do you compare two date objects

How do you check if a string starts with another string

How do you trim a string in javascript

How do you add a key value pair in javascript

Is the !-- notation represents a special operator

How do you assign default values to variables

How do you define multiline strings

What is an app shell model

Can we define properties for functions

What is the way to find the number of parameters expected by a function

What is a polyfill

What are break and continue statements

What are js labels

What are the benefits of keeping declarations at the top

What are the benefits of initializing variables

What are the recommendations to create new object

How do you define JSON arrays

How do you generate random integers

Can you write a random integers function to print integers within a range

What is tree shaking

What is the need of tree shaking

Is it recommended to use eval

What is a Regular Expression

What are the string methods that accept Regular expression

What are modifiers in regular expression

What are regular expression patterns

What is a RegExp object

How do you search a string for a pattern

What is the purpose of exec method

How do you change the style of a HTML element

What would be the result of 1+2+'3'

What is a debugger statement

What is the purpose of breakpoints in debugging

Can I use reserved words as identifiers

How do you detect a mobile browser

How do you detect a mobile browser without regexp

How do you get the image width and height using JS

How do you make synchronous HTTP request

How do you make asynchronous HTTP request

How do you convert date to another timezone in javascript

What are the properties used to get size of window

What is a conditional operator in javascript

Can you apply chaining on conditional operator

What are the ways to execute javascript after a page load

What is the difference between proto and prototype

Can you give an example of when you really need a semicolon

What is the freeze method

What is the purpose of the freeze method

Why do I need to use the freeze method

How do you detect a browser language preference

How to convert a string to title case with javascript

How do you detect if javascript is disabled on the page

What are various operators supported by javascript

What is a rest parameter

What happens if you do not use rest parameter as a last argument

What are the bitwise operators available in javascript

What is a spread operator

How do you determine whether object is frozen or not

How do you determine two values same or not using object

What is the purpose of using object is method

How do you copy properties from one object to other

What are the applications of the assign method

What is a proxy object

What is the purpose of the seal method

What are the applications of the seal method

What are the differences between the freeze and seal methods

How do you determine if an object is sealed or not

How do you get enumerable key and value pairs

What is the main difference between Object.values and Object.entries method

How can you get the list of keys of any object

How do you create an object with a prototype

What is a WeakSet

What are the differences between WeakSet and Set

List down the collection of methods available on WeakSet

What is a WeakMap

What are the differences between WeakMap and Map

List down the collection of methods available on WeakMap

What is the purpose of uneval

How do you encode an URL

How do you decode an URL

How do you print the contents of web page

What is the difference between uneval and eval

What is an anonymous function

What is the precedence order between local and global variables

What are javascript accessors

How do you define property on Object constructor

What is the difference between get and defineProperty

What are the advantages of Getters and Setters

Can I add getters and setters using defineProperty method

What is the purpose of switch-case

What are the conventions to be followed for the usage of switch case

What are primitive data types

What are the different ways to access object properties

What are the function parameter rules

What is an error object

When do you get a syntax error

What are the different error names from error object

What are the various statements in error handling

What are the two types of loops in javascript

What is nodejs

What is the Intl object

How do you perform language specific date and time formatting

What is an Iterator

How does synchronous iteration works

What is the event loop

What is the call stack

What is the event queue

What is a decorator

What are the properties of the Intl object

What is an Unary operator

How do you sort elements in an array

What is the purpose of compareFunction while sorting arrays

How do you reverse an array

How do you find the min and max values in an array

How do you find the min and max values without Math functions

What is an empty statement and purpose of it

How do you get the metadata of a module

What is the comma operator

What is the advantage of the comma operator

What is typescript

What are the differences between javascript and typescript

What are the advantages of typescript over javascript

What is an object initializer

What is a constructor method

What happens if you write constructor more than once in a class

How do you call the constructor of a parent class

How do you get the prototype of an object

What happens If I pass string type for getPrototype method

How do you set the prototype of one object to another

How do you check whether an object can be extended or not

How do you prevent an object from being extend

What are the different ways to make an object non-extensible

How do you define multiple properties on an object

What is the MEAN stack

What is obfuscation in javascript

Why do you need Obfuscation

What is Minification

What are the advantages of minification

What are the differences between obfuscation and Encryption

What are the common tools used for minification

How do you perform form validation using javascript

How do you perform form validation without javascript

What are the DOM methods available for constraint validation

What are the available constraint validation DOM properties

What are the validity properties

Give an example usage of the rangeOverflow property

Are enums available in javascript

What is an enum

How do you list all properties of an object

How do you get property descriptors of an object

What are the attributes provided by a property descriptor

How do you extend classes

How do I modify the url without reloading the page

How do you check whether or not an array includes a particular value

How do you compare scalar arrays

How to get the value from get parameters

How do you print numbers with commas as thousand separators

What is the difference between java and javascript

Does JavaScript support namespaces

How do you declare a namespace

How do you invoke javascript code in an iframe from the parent page

How do you get the timezone offset of a date object

How do you load CSS and JS files dynamically

What are the different methods to find HTML elements in DOM

What is jQuery

What is V8 JavaScript engine

Why do we call javascript as dynamic language

What is a void operator

How to set the cursor to wait

How do you create an infinite loop

Why do you need to avoid with statement

What is the output of the following for loops

List down some of the features of ES6

What is ES6

Can I redeclare let and const variables

Does the const variable make the value immutable

What are default parameters

What are template literals

How do you write multi-line strings in template literals

What are nesting templates

What are tagged templates

What are raw strings

What is destructuring assignment

What are default values in destructuring assignment

How do you swap variables in destructuring assignment

What are enhanced object literals

What are dynamic imports

What are the use cases for dynamic imports

What are typed arrays

What are the advantages of module loaders

What is collation

What is for...of statement

What is the output of below spread operator array

Is PostMessage secure

What are the problems with postmessage target origin as wildcard

How do you avoid receiving postMessages from attackers

Can I avoid using postMessages completely

Is postMessages synchronous

What paradigm is Javascript

What is the difference between internal and external javascript

Is JavaScript faster than server side script

How do you get the status of a checkbox

What is the purpose of double tilde operator

How do you convert character to ASCII code

What is ArrayBuffer

What is the output of below string expression

What is the purpose of Error object

What is the purpose of EvalError object

What are the list of cases error thrown from non-strict mode to strict mode

Do all objects have prototypes

What is the difference between a parameter and an argument

What is the purpose of some method in arrays

How do you combine two or more arrays

What is the difference between Shallow and Deep copy

How do you create specific number of copies of a string

How do you return all matching strings against a regular expression

How do you trim a string at the beginning or ending

What is the output of below console statement with unary operator

Does javascript uses mixins

Mixin Example using Object composition

Benefits

What is a thunk function

What are asynchronous thunks

What is the output of below function calls

How to remove all line breaks from a string

What is the difference between reflow and repaint

What happens with negating an array

What happens if we add two arrays

What is the output of prepend additive operator on falsy values

How do you create self string using special characters

How do you remove falsy values from an array

How do you get unique values of an array

What is destructuring aliases

How do you map the array values without using map method

How do you empty an array

How do you round numbers to certain decimals

What is the easiest way to convert an array to an object

How do you create an array with some data

What are the placeholders from console object

Is it possible to add CSS to console messages

What is the purpose of dir method of console object

Is it possible to debug HTML elements in console

How do you display data in a tabular format using console object

How do you verify that an argument is a Number or not

How do you create copy to clipboard button

What is the shortcut to get timestamp

How do you flattening multi dimensional arrays

What is the easiest multi condition checking

How do you capture browser back button

How do you disable right click in the web page

What are wrapper objects

What is AJAX

What are the different ways to deal with Asynchronous Code

How to cancel a fetch request

What is web speech API

What is minimum timeout throttling

How do you implement zero timeout in modern browsers

What are tasks in event loop

What is microtask

What are different event loops

What is the purpose of queueMicrotask

How do you use javascript libraries in typescript file

What are the differences between promises and observables

What is heap

What is an event table

What is a microTask queue

What is the difference between shim and polyfill

How do you detect primitive or non primitive value type

What is babel

Is Node.js completely single threaded

What are the common use cases of observables

What is RxJS

What is the difference between Function constructor and function declaration

What is a Short circuit condition

What is the easiest way to resize an array

What is an observable

What is the difference between function and class declarations

What is an async function

How do you prevent promises swallowing errors

What is deno

How do you make an object iterable in javascript

What is a Proper Tail Call

How do you check an object is a promise or not

How to detect if a function is called as constructor

What are the differences between arguments object and rest parameter

What are the differences between spread operator and rest parameter

What are the different kinds of generators

What are the built-in iterables

What are the differences between for...of and for...in statements

How do you define instance and non-instance properties

What is the difference between isNaN and Number.isNaN?

How to invoke an IIFE without any extra brackets?

Is that possible to use expressions in switch cases?

What is the easiest way to ignore promise errors?

How do style the console output using CSS?

What is nullish coalescing operator (??)?

How do you group and nest console output?

What is the difference between dense and sparse arrays?

What are the different ways to create sparse arrays?

What is the difference between setTimeout, setImmediate and process.nextTick?

How do you reverse an array without modifying original array?

How do you create custom HTML element?

What is global execution context?

What is function execution context?

What is debouncing?

What is throttling?

What is optional chaining?

What is an environment record?

How to verify if a variable is an array?

What is pass by value and pass by reference?

What are the differences between primitives and non-primitives?

How do you create your own bind method using either call or apply method?

What are the differences between pure and impure functions?

What is referential transparency?

What are the possible side-effects in javascript?

What are compose and pipe functions?

What is module pattern?

What is Function Composition?

How to use await outside of async function prior to ES2022?

What is the purpose of the this keyword in JavaScript?

What are the uses of closures?

What are the phases of execution context?

What are the possible reasons for memory leaks?

What are the optimization techniques of V8 engine?

What are the examples of built-in higher order functions?

What are the benefits higher order functions?

How do you create polyfills for map, filter and reduce methods?

What is the difference between map and forEach functions?

Give an example of statements affected by automatic semicolon insertion?

What are the event phases of a browser?

What are the real world use cases of proxy?

What are hidden classes?

What is inline caching?

What are the different ways to execute external scripts?

What is Lexical Scope?

How to detect system dark mode in javascript?

What is the purpose of requestAnimationFrame method?

What is the difference between substring and substr methods?

How to find the number of parameters expected by a function?

What is globalThis, and what is the importance of it?

What are the array mutation methods?

What is module scope in JavaScript?

What are shadowing and illegal shadowing?

Why is it important to remove event listeners after use?

What is structuredClone and how is it used for deep copying objects?

What is the difference between const and Object.freeze

What is Promise.any and when should it be used?

What is BigInt and how is it different from Number?

What are private class fields in JavaScript?

What is the Array.prototype.at() method and why is it useful?

What is top-level await in JavaScript modules?

What are WeakRef and FinalizationRegistry used for?

What are logical assignment operators?

What is the Temporal API and why is it proposed as a replacement for Date?

What is the difference between for loop and forEach

What are Symbols and what are their use cases?

What is the difference between Object.create() and Object.assign()?

What are generator functions and how do they work?

What is the Reflect API and when should you use it?

How does JavaScript handle floating point precision issues?

What are tagged template literals and their practical uses?

What is the difference between Object.keys(), Object.values(), and Object.entries()?

What is the Intl.NumberFormat API and how is it used?

How do you implement method chaining in JavaScript?

What are the differences between Map and Object for storing key-value pairs?

What is the purpose of Symbol.iterator and how do you use it?

How does the Intersection Observer API work?

What are async iterators and how are they different from regular iterators?

What is the purpose of Object.getOwnPropertyDescriptors()?

How does Promise.allSettled() differ from Promise.all()?

What are the performance implications of using try-catch in JavaScript?

What is the AbortController API and how is it used?

How do you implement a custom error class in JavaScript?

What is the difference between synchronous and asynchronous generators?

What are Proxy traps and what operations can they intercept?

How does the Mutation Observer API work?

What is tail call optimization and does JavaScript support it?

What are the different ways to handle circular references in JSON?

How do you implement a singleton pattern in JavaScript?

What is the Performance API and how is it used for measuring performance?

What are the differences between SharedArrayBuffer and ArrayBuffer?

How do you prevent prototype pollution attacks in JavaScript?

What is the Atomics API and when should it be used?

How do you implement a lazy loading pattern for modules?

What are the best practices for optimizing JavaScript bundle size?