React JS – A Deep Dive

Explore every file and folder in a React project and learn why each item is required through detailed explanations.

Explore the default React project structure by inspecting the app folder and core directories like src and public in the VS Code explorer, including key files such as package.json.

Explore how package.json documents project dependencies, libraries, and their versions, and learn how this configuration file manages the software tools used by your React project.

Explore how software version numbers use major, minor, and patch components to indicate backward compatibility, with major versions signaling backward incompatibility and patch updates maintaining compatibility.

Explore the caret symbol (^) in versioning, learn how it fixes the major version while allowing minor and patch updates, and understand compatibility with other dependencies.

Explore how node_modules organizes dependency libraries in folders for a React js project, driven by package.json, and how actual software is downloaded and kept in the node_modules directory.

Explore how package.json defines dependency information and versions, while package-lock.json records exact downloaded dependencies for runtime, guiding installation and conflict checks in production.

Learn how to use the .gitignore file to prevent pushing unnecessary files and folders, including node_modules and config files, to your git repository and cloud deployments.

Learn how to reset and install dependencies by removing node_modules and package-lock.json, then run npm install (or npm i) to download dependencies listed in package.json into node_modules.

Remove node_modules and package-lock.json, reinstall dependencies via npm install based on package.json, then start the project with npm start to verify it runs successfully.

Learn how the public folder in a React app exposes its contents to browsers worldwide, and see how files like robots.txt, manifest.json, and logo become accessible via a browser.

Access any file from the browser by using the public folder, including favicon.ico, since any file placed in the public folder is accessible via the browser.

Create and organize new files and folders in the public folder, such as person.json, and access them directly from the browser.

discover how the welcome file automatically runs when you request an application without specifying a file name, and how it executes at localhost:3000.

Discover how index.html acts as the welcome file in the public folder. Defines a div with id root for mounting via index.js on port 3000.

Explore requests to an unavailable resource in the public folder and how the welcome file handles them. Show how the default welcome file responds to missing resources of any extension.

Learn how to rename your React app's title by editing index.html, then see the updated title in the browser while exploring the app.

Explore how developer code resides in the CRC and src folders, with app.js and index.js containing programming content, and all components built inside the src folder for a React project.

Analyze how index.js wires a route from index.html to the app component, rendering the same route content through the app component.

Understand that a component is a piece of reusable code you develop once and reuse wherever required, enabling code reuse across multiple places in React JS development.

Explore the four core features of a web component in React: programming task execution and processing, presenting results to customers with a rich look and feel, and testing.

Explore the web component's file structure with JavaScript or TypeScript, HTML presentation, and Bootstrap CSS to achieve a rich look and feel while comparing four-file architecture to React's three-file setup.

Explore how a default app component is created automatically in a React project, organized under the src folder with app.js, app.css, and app.test.js for programming, styling, and testing.

Modify react app components by editing app.js, adjusting return and div content, removing headers, and updating root rendering in index.html and index.js to see changes reflected in browser without restarting.

Reuse the app component across multiple instances, rendering it in index.js, and learn that the app is a default, reusable component any number of times.

Import index.css in index.js to apply its CSS classes globally across the entire application. Set a sample style, like color blue, to demonstrate the global CSS configuration.

Import logo.svg with an identifier in src, alias it in code, and render it in App.js using an image tag, then verify the logo appears in the browser.

Explore the presentation portion of the app component by organizing content into a single root tag with optional child tags, such as an h1 styled with a blue CSS class.

Explore essential JavaScript concepts—var, let, const, arrays, JSON objects, and arrays of JSON—plus events, preventDefault, stopPropagation, and import/export patterns that every React component relies on.

Learn to create a new React application using npx and create-react-app, initialize an app named App3, and open it in VSCode as the project is ready.

Master the var keyword for declaring variables in JavaScript, examine function-level scope versus block scope, and learn how redeclaration works with practical console.log examples.

Explore the let variable in JavaScript, its block scope and local binding, contrast with var, and explain why redeclaration is not allowed - essential for interviews.

Explore JavaScript const declarations, demonstrating that constants cannot be reassigned and have block scope. Learn differences between let and const, including redeclaration rules and how constants restrict reinitialization.

Explore JavaScript arrays, including declaring with const, let, or var, reinitialization concepts, and printing array content of same or different types using the join method with separators.

Learn to create and display json objects using JavaScript object notation, including two objects—a student and a product—each with key-value fields grouped together.

Explore an array of JSON objects by using the map function to read and display each student's details, with three members and a focus on identifiers and map syntax.

Learn javascript events, focusing on on click, on change, and on submit; attach on click to a button to execute a function and log messages to the console.

Compare two hyperlinks to show how an onclick handler calls preventDefault to stop the browser from navigating, while the other link goes to google.com.

Explore stop propagation in React events by preventing a child's click from triggering its parent using event.stopPropagation, illustrated with test1 and test2 in a div and h1 structure.

Learn how to declare javascript functions using the function keyword, define statements, call them from a button, and handle any number of arguments and optional returns.

Explore defining JavaScript functions using expressions as a second approach, including constants and arguments. See tests execute in the console and compare with declaration methods.

Learn how to define JavaScript functions using arrow syntax, including using const, omitting the function keyword, and employing arrow functions for modern, browser-ready code.

Understand how to export and import JavaScript module members, export functions f1 and f2, and use them across files, while also exporting constants and variables from a single file.

Explore default and non-default exports in a React JS context, learn how to declare a single default export per file, and contrast direct default imports with named exports in modules.

Learn how to import default and named exports in React by importing default exports directly and named exports inside curly braces, ensuring all modules are imported before use.

Learn how to integrate JavaScript and CSS inside the app component, showing practical examples of using JavaScript code and CSS code within a React app.

Identify locations to place JavaScript code inside a React app component: before the app function, inside the app function before return, after the app function before export, and after export.

Learn how to declare and use JavaScript variables inside a React app component, covering four locations—before return, inside the app function, before export, and after export.

Explore how to declare, define, and use JavaScript functions inside a React app component. The lecture shows four functions around the app component, each returning a value that is printed.

Declare a JSON object and use it inside the app component before the return statement, illustrating how to integrate JavaScript programming within the app function.

Declare and use JavaScript arrays inside a React app component function, demonstrating basic array operations and joining elements before returning the component.

Learn how the JavaScript array map function iterates element by element to provide the specified mapping, including mappings with the p element and the div element, in the browser.

Explore how to use the forEach method with JavaScript arrays to print each element to the console rather than render in the browser.

Iterate over an array of JSON objects in React, map each object to display name and age, and diagnose a common mistake of a missing function implementation.

Apply a css class to the h1 element in the app component and import app.css to style the heading, showcasing blue color styling from the stylesheet.

Discover how app.css takes precedence over index.css for component styling in a React app, with index.css providing global fallback styles such as h1 color choices.

Master creating and reusing components in React JS, applying CSS to components, and understanding the CSS order with component CSS and CSS index CSS from scratch.

Create a new React component in student.js, export it as default, and import it into app.js to render a hello world presentation in the app component.

Add styles to the student component by creating a dedicated student.css file and importing it into the component. Style the h1 with a red color to apply consistent design.

Practice repeating component usage in React by rendering the same component multiple times, with a single parent element inside a return, and using the student component as needed.

This lecture demonstrates how css file order determines styling priority, showing how student.css, app.css, and index.css influence colors through imports and fallbacks.

Create and reuse multiple React components by exporting default functions, importing and using them across the app, and rendering the same component many times, with CSS from index.js.

Discover the concept of hooks in React and identify two widely used hooks. Understand how these two predefined features function in React usage.

Discover how to manage state with useState in a React app by declaring i and j with initial values, updating them only through their setters, and observing UI re-renders.

Explore how useEffect initializes data on app start or during navigation, coordinating with useState to run code automatically when the component loads.

Create a json file named person.json in the public folder containing an array of objects with name and age, and read this data into the component.

Discover how members of a public folder can be accessed from the browser address bar.

Load json file into a React component by fetching persons.json in useEffect and storing data in state with setPersons, executing once when the app loads.

Learn to render json objects from a json file in React, using map to display each person from the persons array with name and age, and manage state with useEffect.

Explore form development in React by building a practical form with text fields, password fields, text areas, and dropdown controls, focusing on form fields and form controls.

Explore the differences between input type='button' and the button tag, noting content inside the tag versus a self-contained input, CSS decoration, and the default submit behavior when using button elements.

Build a simple React component with a text field using useState to bind the value to firstName, showing the value when present and noting that placeholders don't display.

Learn to handle the onClick event in React and print data to the console. Use state for a field, update a TextField, and print first name via a button click.

Understand how placeholders and values work in input fields, seeing that placeholders display only when there is no value and that a default value eliminates the placeholder.

Develop a password field component in React by creating individual state for each field, handling onClick and onChange events, and validating the input against the password.

Learn how to manage a textarea in React by tying it to an address state, updating via onChange, and printing data onClick with a placeholder example.

Explore building a React component with a date field, managing state, and handling on change and on click to print data and save it in the browser.

Implement a datetime-local field in a React component, using state to manage the date and time values, with placeholder and type handling.

Demonstrate building a select dropdown in a React component, handling onclick and onchange events, retrieving currentTarget.value, and logging the selected options like M.Tech, B.Tech, MBA to the console.

Manage several form fields in one React component by assigning a useState for each field (text, password, textarea, select) and print all values on click, including first name and region.

Demonstrate reading form fields into a JSON object in React by capturing first name, password, address, and education, then logging the JSON and its fields to the browser console.

Create a React component for a simple signup form with three fields—first name, email, and password—wired to a function and a button that outputs a JSON object.

Build a simple login form that uses email and password, prints a JSON object to the browser console, illustrating basic data handling in React JS.

Explore JavaScript arrays and essential methods like map, filter, reduce, and includes, plus JSON conversions between strings and objects, to establish the foundation for React.js.

Revise javascript arrays in a react app by using use state to manage arrays, printing with join, and comparing arrays with use state to see changes reflect in the ui.

Explore the JavaScript array map method using an arrow function with element and index. See how map returns a new array without mutating original and why unique key is advised.

Explore JavaScript's filter method with a two-argument callback to produce a new array by boolean condition, then chain map and filters for values greater than 20 and divisible by ten.

Explore how the JavaScript reduce method processes arrays to produce a single result, such as sum, product, min, or max, by iterating with an accumulator and current value.

Sort numeric arrays in ascending order using an arrow function with a difference to decide order, then store the sorted results in an array and update state to reflect changes.

Sort numeric arrays in descending order using the array sort method with the comparator b minus a. This simple, reverse order approach completes the task quickly.

Sort a string array in ascending order using the locale compare function within the built-in sort, with an arrow function as the callback to compare elements.

Explore converting a JSON object into a string using the stringify method, and observe how a JSON object becomes a string.

Discover how to search a string array in React JS by filtering elements that contain a given character using the includes method, demonstrating a practical search workflow.

Explore searching for an element in a numeric array and converting the array to a string in React JS. See how includes checks for numbers and strings.

Explore how a JSON object initializes a user state as initial content and how to print and use that object through state to access name and gender.

Explore how a JSON object converts to a string using the JSON.stringify method, observing the stringify process on a sample object in this React JS deep dive.

Learn how to convert strings to JSON objects using JSON.parse, then convert them back to strings, and access fields like name, age, and gender in React JS.

Learn how to retrieve all keys from a JSON object using Object.keys, print them as an array, and map over them to display each key with its value.

Learn how object.values(obj) retrieves all values from a JSON object, print them one by one or via map, and read only the values stored in the object.

Explore how Object.entries(obj) returns a two-dimensional array of key-value pairs from a JSON object, with each entry as a [key, value] subarray, enabling map-based iteration.

Explore how object.assign copies enumerable properties from source to target; after combining person two into person one, both person one and person three hold name, age, gender, weight, height.

Explore spread syntax in React JS by using the spread operator to merge objects and add new keys, and see updates flow to person two via a setter.

Explore deleting a json key or entry by moving data to another array, using delete, and updating person objects with a change data function to reflect removed fields like age.

Explore composing radio buttons, checkboxes, file inputs, and multi-select dropdowns to build complex form fields in React.

Create a React component with radio buttons to select gender, manage a gender state, and print the chosen value to the console using hardcoded male and female options.

Learn how to render radio buttons from reference data using arrays and map in React JS, iterating genders and binding dynamic values for male and female options.

Render radio buttons from a JSON array of gender objects by mapping to a radio with value as the gender id and label as the gender name, highlighting id values.

Learn to manage multiple checkboxes to build a dynamic selected skills list, updating via onChange, adding or removing values with spread and filter operators.

Learn how to implement a shared onChange handler for all checkboxes in React JS, enabling adding or removing skills as users check or uncheck options, with console logging.

Render one checkbox per skill from a reference skills array by mapping each skill. Handle selection and unselection with if/else blocks, causing removal on uncheck and logging changes to console.

Learn to implement checkboxes with a JSON object reference data, iterating the skills array and using id for value and name for display, with console IDs shown.

Explore a multi select dropdown component in React, printing selected options and mapping them to extract only their values, then update the selected educations state.

Build a multi select box with reference data, generate each option using the map method, and update a map of selected options on change to reflect chosen education or skills.

Learn to build a multi-select component with JSON objects as reference data, using an education array of objects with id and name to map option values and the label purpose.

Explore a React js component for uploading a single file, handling on change, accessing e.target.files[0], printing file information to console, and preparing data for server upload and database storage later.

Learn to implement a single component that handles selecting and uploading multiple files, including a resume and profile picture, with console feedback and server upload flow.

Demonstrate building a React file upload component that supports selecting multiple files in one field using input type file and the multiple attribute.

Build a signup form in React js with fields: first name, last name, age, email, gender radios, education, address, skills checkboxes, and profile picture upload, logging data to console.

Explore form validations in React across text, password, radio, textarea, date, time, dropdowns, checkboxes, and file inputs to ensure required fields like first name, last name, and email are filled.

Learn extra field validation in React JS by validating the first name on submit, showing errors in red via a span, and updating or clearing messages with state.

Learn to validate a password field in React JS by using state to show or remove a password error, and render the same error in a red span.

Learn how to implement textarea field validation in React, enforce a required address, display error messages, and handle submission with real-time feedback.

Master date field validation in React JS by handling the date of join, setting and removing errors, and ensuring submission with DOJ required.

Explore datetime field validation in React JS, ensure that date of birth is required, the date and time are valid, and error messages are clear during submission.

Audit email field validation with the required rule, identify and handle email errors, and ensure proper form submission.

Explore basic email validation using a regular expression, detailing local-part rules, the at symbol, domain, and dot escaping to ensure a valid email format.

Learn how radiobutton validation works: display a gender error when none is selected and remove the error once a gender is chosen and the form is submitted.

Validate checkbox selections for skills in a React app, manage selected skills in a set, enforce at least one selection on submit, and display a skills required error.

Learn to validate a select dropdown in React, handle education error states, require a value, and verify behavior in the browser by submitting.

Validate multi select education options in a React JS app by ensuring at least one option is selected through a multi select dropdown, with SSC or HSC choices.

Explore file upload validation for a resume field in React JS: verify whether a resume is selected, display or clear errors, and enable submit only when a file is chosen.

Learn how to handle a multiple file input in React, allowing users to select multiple files. Enforce a minimum of one file and apply a consistent validation procedure before submitting.

Build a simple sign-up form in a single component, validate first name, username, and password using three useState hooks, display per-field errors, and submit to a server-side API.

Create a simple signup form in React with validations for first name, username, and password, and manage focus using useRef for the first invalid field.

Implement simple signup form validations using a single user object and a local address object, manage focus with refs, handle a centralized errors object, and submit when all fields validate.

Explore a simple signup flow in React JS with validations, errors object, and a submit alert, using local and global address to validate first and last name before submission.

Validate a simple login form with username and password, using a global address object to store multiple entries and local validation before submission.

Learn to implement a simple login form with validations and focus management using useRef, including local error handling, conditional focusing, and conditional submit.