Notas de Estudio de JavaScript

JavaScript Study Notes

• JavaScript is an interpreted programming language, a dialect of ECMAScript.
• It's object-oriented, prototype-based, imperative, and dynamically typed.
• It's not compiled; however, it can be compiled Just-In-Time (JIT) in some engines.
• Modern JavaScript recommends using let for changing variables and const for unchanging ones.
• Anonymous functions are functions without names, often assigned to variables or passed as arguments.

Variables and Operators

• The === operator compares both value and type of operands, unlike == which only compares values.

Promises

• A promise in JavaScript represents the eventual completion or failure of an asynchronous operation.
• Promises allow elegant handling of future results.
• They resolve or reject when the operation is finished.
• A promise executes through its then method.

JSON

• JSON (JavaScript Object Notation) is a lightweight data-interchange format.
• It's human-readable and can be easily analyzed and generated by machines.
• It's commonly used for data exchange between systems.

Fetch API

• fetch is a method for asynchronous HTTP requests to get data from a server.

HTTP Methods (POST & GET)

• GET requests data from a server.
• POST sends data to a server.

Arrays and console.log output

• Arrays are considered objects in JavaScript.
• typeof [] returns "object".
• Use push() to add elements to the end of an array (returns the new length of the array).

Hoisting

• JavaScript's hoisting behavior moves variable and function declarations to the top of their scope.

Event Bubbling

• Event bubbling is a DOM event propagation method where an inner element's triggered event travels up the parent elements in the DOM tree.

Array.prototype.map()

• Creates a new array with the results of applying a function to each array element.

Array.prototype.reduce()

• Executes a reducer function (that you provide) on each element of the array, resulting in a single output value.

Closures

• A closure combines a function and its lexical environment.
• It allows a function to access variables from its outer scope, even after the outer function has finished.

Module Pattern

• A pattern for encapsulating related functionalities into a single object, providing privacy and organization.

DOM

• The Document Object Model (DOM) is a programming interface for HTML and XML documents.
• It represents the document as a tree of objects, allowing interaction and modification of the HTML structure.
• The DOM is an API.

DOMContentLoaded Event

• This event fires when the initial HTML document has loaded and parsed completely.

load Event

• The load event fires when everything (including images, scripts, and stylesheets) has finished loading.

Arrow Functions

• Arrow functions are a concise way to create functions in JavaScript and have lexically scoped behavior of this.

use strict

• Turning on strict mode for JavaScript using use strict enforces rules, leading to more secure and optimized code.

AJAX

• Asynchronous JavaScript and XML (AJAX) is a web development technique to update parts of a web page without reloading.

forEach method

• Iterates over an array and applies a provided function to each element.

Event Listener (addEventListener)

• addEventListener allows you to assign a function to be executed when a specific event occurs on an element.

Classes (e.g., mt)

• CSS classes (mt, mb, ml, mr, etc.) are used for applying margins.
• They can be combined in a variety of ways to apply various margins.

findIndex & find Methods

• findIndex returns the index of the first element in an array that satisfies a provided testing function.
• find returns the first element that satisfies a condition in an array.

includes Method

• Verifies if a specified element exists in an array or string, returning true or false.

collapse Class

• collapse is a class (often used in frameworks like Bootstrap) that controls the visibility of an element (usually content) by switching classes in an animation.

classList.toggle("active")

• This toggles the presence of the active class on an element.

Local Storage

• Browser storage that lets you save key-value pairs persistently.

JSON.stringify() & JSON.parse()

• JSON.stringify() converts an object to a JSON string.
• JSON.parse() converts a JSON string back to an object.

parseFloat

• Converts a string to a floating-point number.

this Keyword

• this in JavaScript can refer to different objects depending on how the function is called.

reduce Method

• reduce applies a function cumulatively to the array elements, reducing them to a single value.

Server-Side Rendering (SSR)

• In web development, server-side rendering is a technique of generating the HTML of a page on the server instead of the client-side JavaScript. Server-side rendering is often used to help performance.

Time To Interactive (TTI)

• TTI is the point where the web page has loaded and can respond to user interaction (visual rendering and responsiveness).

Transactions

• Database transactions ensure atomicity; either they complete fully or not at all, maintaining data consistency even during failures.

Singleton Pattern

• A design pattern that ensures that only one instance of a class can be created and provides global access to it.

Flexbox

• A CSS layout module that allows flexible and efficient layout by defining and controlling how items are positioned and aligned within a container.

Microservices

• An architectural style where an application is structured as a collection of loosely coupled services each handling a specific part of the functionality.

Webpack

• A module bundler for modern JavaScript applications that handles dependencies and creates bundles for consumption.

React Hooks

• Hooks give functional components in React access to features that were previously only possible in class components, with access to the state and lifecycle.

Test-Driven Development (TDD)

• A software development process where you write tests first, then implement the code to pass the tests.

Sharding

• A technique to divide databases into smaller chunks, called shards, to improve performance and scalability.

JSON Web Token (JWT)

• A compact and self-contained way to transmit information securely between parties, often used for authentication.

Deadlock

• A situation in concurrent programming where two or more processes freeze, each waiting for the other to release a resource.

A/B Testing

• A method for comparing two versions of a webpage to see which performs better.

SQL Injection

• A type of attack on web applications where an attacker inserts malicious SQL code into input fields.

Progressive Web Apps (PWAs)

• Applications that use web technologies and offer a native-like experience on mobile and desktop, with offline functionality and push notifications.

Model-View-Controller (MVC)

• A software design pattern that separates an application's concerns into separate modules. The Model manages the data and business logic, the View is the user interface, and the Controller manages user interactions and updates the model and view as needed.

Media Queries

• CSS rules that apply different styles based on the characteristics of the device or screen on which the page is being displayed, useful for responsiveness on different screen sizes.

Este cuestionario evalúa tus conocimientos sobre JavaScript, incluyendo conceptos clave como variables, operadores y promesas. También abarca el uso de JSON como un formato de intercambio de datos. Ponte a prueba y mejora tu comprensión de esta popular lengua de programación.