Introduction

JavaScript is a versatile, high-level programming language primarily used for web development. It enables interactive web pages and is an essential part of web applications. JavaScript is easy to learn for beginners but has deep and powerful capabilities for experienced developers.

Grammar and Types

Basic Syntax

JavaScript programs are composed of statements, which are instructions to be executed.

letx=10;console.log(x);// Outputs: 10

Data Types

JavaScript supports various data types, including:

• Primitive Types:String,Number,Boolean,Null,Undefined,Symbol, andBigInt.

letstr="Hello, World!";letnum=42;letisActive=true;

Variables

Variables in JavaScript can be declared usingvar,let, orconst.

• var has function scope.
• let andconst have block scope, withconst being used for constants.

letage=25;constPI=3.14;

Control Flow and Error Handling

Conditionals

Conditionals control the flow of execution based on conditions.

• If-else Statements:

letage=18;if(age>=18){console.log("Adult");}else{console.log("Minor");}

Error Handling

Error handling is crucial for managing exceptions and ensuring smooth execution.

• Try-Catch-Finally:

try{thrownewError("Something went wrong!");}catch(error){console.error(error.message);}finally{console.log("Execution complete.");}

Loops and Iteration

For Loop

For loops are used for iterating over a block of code a number of times.

• Basic For Loop:

for(leti=0;i<5;i++){console.log(i);// Outputs: 0, 1, 2, 3, 4}

While Loop

While loops continue to execute as long as a specified condition is true.

• Basic While Loop:

leti=0;while(i<5){console.log(i);// Outputs: 0, 1, 2, 3, 4i++;}

Functions

Declaration and Invocation

Functions are reusable blocks of code that perform a specific task.

• Function Declaration:

functiongreet(name){return`Hello,${name}!`;}console.log(greet("Alice"));// Outputs: Hello, Alice!

Arrow Functions

Arrow functions provide a shorter syntax for writing functions.

• Arrow Function Syntax:

constadd=(a,b)=>a+b;console.log(add(2,3));// Outputs: 5

Expressions and Operators

Arithmetic Operators

Arithmetic operators are used to perform mathematical operations.

• Basic Arithmetic:

letsum=5+3;// 8letproduct=4*2;// 8

Logical Operators

Logical operators are used to combine or invert Boolean values.

• AND, OR, NOT:

letisAdult=true;lethasID=false;console.log(isAdult&&hasID);// falseconsole.log(isAdult||hasID);// true

Numbers and Dates

Working with Numbers

JavaScript provides various methods to handle numbers effectively.

• Basic Operations:

letnum=123.456;console.log(num.toFixed(2));// "123.46"

Working with Dates

The Date object is used to work with dates and times.

• Date Object:

letnow=newDate();console.log(now.toISOString());// Outputs current date and time in ISO format

Text Formatting

String Methods

Strings can be manipulated using various built-in methods.

• Manipulating Strings:

letmessage="Hello, World!";console.log(message.toUpperCase());// "HELLO, WORLD!"console.log(message.slice(0,5));// "Hello"

Regular Expressions

Pattern Matching

Regular expressions are patterns used to match character combinations in strings.

• Using Regex:

letpattern=/world/i;lettext="Hello, World!";console.log(pattern.test(text));// true

Indexed Collections

Arrays

Arrays are list-like objects used to store multiple values.

• Basic Array Operations:

letfruits=["Apple","Banana","Cherry"];console.log(fruits.length);// 3console.log(fruits[1]);// "Banana"

Keyed Collections

Objects

Objects are collections of key-value pairs.

• Creating and Accessing Objects:

letperson={name:"Alice",age:30};console.log(person.name);// "Alice"

Maps

Maps are collections of keyed data items, like objects but with better performance for frequent additions and removals.

• Map Object:

letmap=newMap();map.set("key1","value1");console.log(map.get("key1"));// "value1"

Working with Objects

Object Methods

Objects can have methods, which are functions associated with the object.

• Manipulating Objects:

letcar={brand:"Toyota",model:"Corolla"};car.year=2020;console.log(car);

Using Classes

Class Syntax

Classes provide a blueprint for creating objects.

• Creating Classes:

classAnimal{constructor(name){this.name=name;}speak(){console.log(`${this.name} makes a noise.`);}}letdog=newAnimal("Dog");dog.speak();// "Dog makes a noise."

Using Promises

Promise Syntax

Promises represent the eventual completion (or failure) of an asynchronous operation.

• Handling Asynchronous Operations:

letpromise=newPromise((resolve,reject)=>{letsuccess=true;if(success){resolve("Operation successful!");}else{reject("Operation failed.");}});promise.then(message=>{console.log(message);// Outputs: Operation successful!}).catch(error=>{console.error(error);});

JavaScript Typed Arrays

Typed Array Basics

Typed arrays provide a mechanism for accessing raw binary data.

• Using Typed Arrays:

letbuffer=newArrayBuffer(16);letint32View=newInt32Array(buffer);int32View[0]=42;console.log(int32View[0]);// 42

Iterators and Generators

Iterator Protocol

The iterator protocol allows objects to define or customize their iteration behavior.

• Creating Iterators:

letiterable={[Symbol.iterator](){letstep=0;return{next(){step++;if(step<=5){return{value:step,done:false};}else{return{done:true};}}};}};for(letvalueofiterable){console.log(value);// Outputs: 1, 2, 3, 4, 5}

Generators

Generators simplify the creation of iterators by providing a function-based syntax.

• Generator Function:

function*generator(){yield1;yield2;yield3;}letgen=generator();console.log(gen.next().value);// 1console.log(gen.next().value);// 2console.log(gen.next().value);// 3

Meta Programming

Proxy

Proxies enable the creation of objects with custom behavior for fundamental operations.

• Using Proxies:

lettarget={};lethandler={get:function(obj,prop){returnpropinobj?obj[prop]:42;}};letproxy=newProxy(target,handler);console.log(proxy.nonExistentProperty);// 42

JavaScript Modules

Module Syntax

Modules allow you to organize code by exporting and importing functionality across different files.

• Import and Export:

// module.jsexportconstgreet=(name)=>`Hello,${name}!`;// main.jsimport{greet}from'./module.js';console.log(greet('Alice'));// Outputs: Hello, Alice!

By mastering these core concepts and features of JavaScript, you'll be