JavaScript fundamentals covers the core building blocks of the language, including variables, operators, data types, data structures, and basic syntax essential for any JS developer.
Node.js console.log() Method
The console.log() method helps us debug JavaScript applications by printing variables or messages to the console. We can use it for various purposes, such as logging errors, strings, messages, functions, objects, and arrays. This method is essential for tracking code execution and understanding program behavior.
JavaScript Variables
In JavaScript, variables are containers that store different types of values. There are generally three ways to declare variables: var (traditional), let (block-scoped, introduced in ES6), and const (immutable, also from ES6). There are also variable naming rules and methods for initializing and changing variable values.
JavaScript Operators
JavaScript operators perform operations on variables and values. We use arithmetic operators for math calculations, assignment operators to assign values, comparison operators to compare values, and logical operators for boolean operations. We can also use string operators to join text and conditional operators for quick decisions.
JavaScript Boolean
Boolean in JavaScript represents true or false values. We can create boolean values directly or through expressions that evaluate to true/false. Boolean objects can be created using the Boolean constructor. Boolean values are useful in conditional statements and logical operations to control program flow.
JavaScript null and undefined
JavaScript has two special primitive data types: null and undefined. Undefined is automatically assigned when we declare variables without values, while null is intentionally assigned to indicate absence of value. Though they seem similar and compare equal with ==, they have different types and are not equal with ===.
JavaScript if…else Conditional Statement
Conditional statements help us make decisions in our code. We use if statements when conditions are true and else statements when false. We can chain multiple conditions with else if. These statements control program flow based on different conditions like checking if numbers are even/odd or determining time of day.
JavaScript Switch Case
Switch case provides an alternative to multiple if-else statements. We compare a single expression against multiple case values and execute matching code blocks. We must include break statements to prevent fall-through behavior. The default case handles situations when no cases match our expression value.
JavaScript Strict Mode
Strict mode helps us write secure JavaScript code by making hidden errors visible. We activate it by adding ‘use strict’ at the beginning of scripts or functions. It prevents using undeclared variables, deleting objects, duplicating parameter names and other potentially problematic practices that JavaScript would normally allow silently.
JavaScript Array
JavaScript arrays store multiple data types together without fixed length or type restrictions. We can declare arrays using literals or the Array class, access elements by index, add elements with push(), remove with pop() and loop through arrays. Arrays in JavaScript are actually objects with special properties.
JavaScript Array reduce() Method
Array transformation methods simplify complex data operations in JavaScript. This guide explains the powerful reduce() method which processes array elements into a single value, covering its syntax, parameters, return values, and practical examples including finding maximum/minimum values and calculating sums of numerical data.
JavaScript Object
JavaScript objects are fundamental non-primitive data types containing key-value pairs. We can create objects using object literals, object class, user-defined classes or constructor functions. Objects can have multiple methods and properties that are accessed using dot notation or bracket notation. They form the core of JavaScript programming.
JavaScript Date Objects
The Date object provides date and time information independent of platform. We can create Date objects in four ways: new Date(), with milliseconds, with a date string, or with specific date components. The article demonstrates various date methods and builds a real-time clock application.
Sets in JavaScript
Collection data structures provide efficient ways to manage unique values in JavaScript. This comprehensive exploration of the Set object covers creating sets, adding and removing elements, checking for value existence, iterating through collections, and performing common set operations like union, intersection, and difference.
JavaScript String Interpolation
String interpolation lets us embed expressions within string literals. We use template literals with backticks (`) and ${expression} syntax to insert variables into strings. This makes our code cleaner than traditional concatenation. We can include multiline strings and perform calculations inside the expressions.
Javascript Random Number Generator
Random numbers are useful for verification codes, CAPTCHAs, random selections and object IDs. We generate random numbers in JavaScript using Math.random() which produces values between 0 and 1. By applying simple math operations and Math.floor(), we can create random integers within specific ranges.
Scope in JavaScript
Scope defines where variables can be accessed in our code. We have four types: block scope (let/const within {}), function scope (variables inside functions), local scope (variables in any block), and global scope (variables accessible everywhere). Understanding scope helps us avoid variable conflicts and write better code.
JavaScript Error Handling
Error handling in JavaScript uses try-catch-finally blocks to manage exceptions. We put code that might cause errors in the try block, handle errors in the catch block, and execute cleanup code in the finally block. We can check error types and create custom errors using the throw keyword.
Classes in JavaScript
Classes in JavaScript provide blueprints for creating objects with shared properties and methods. We use them to implement Object-Oriented Programming principles. Before ES6 introduced classes, constructor functions were used. Classes contain constructors to initialize objects and can include multiple methods accessible through their instances.
Inheritance in JavaScript
Inheritance allows us to create new classes based on existing ones. We use the extends keyword to inherit properties and methods from parent classes. We can override parent methods and use super() to call parent constructors. JavaScript supports prototypal inheritance which differs from classical inheritance in other languages.