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Javascript Tech

Closures in JavaScript

A closure in JavaScript is a function that has access to variables in its outer scope, even after the outer function has returned. A closure is created when a function is defined inside another function and the inner function references variables in the outer function’s scope.

Closures allow you to preserve the state of a function’s variables even after the function has returned, and they can be used to create powerful and flexible functions that can be reused in different parts of your code.

Here’s a simple example of a closure in JavaScript:

function outerFunction(x) {
return function innerFunction(y) {
return x + y;
}
}

const add5 = outerFunction(5);
console.log(add5(3)); // 8

In this example, the outerFunction returns the innerFunction, which has access to the x variable in its outer scope. When we call outerFunction(5), it returns the innerFunction with x set to 5, and we assign it to the add5 variable. When we later call add5(3), it returns the result of x + y, which is 8.

Closures are an important concept in JavaScript, as they can be used to create functions that have private variables, to implement object-oriented concepts like classes and prototypes, and to manage state and data in complex applications.

Source: AI Interaction Channel

Happy Learning!

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Blog Learning Learning

Picture tag in HTML

The <picture> tag in HTML is a semantic element that is used to define multiple source images for a single content. The <picture> element is used to specify multiple sources for an image, allowing the browser to choose the most appropriate source based on the user’s device and screen size. This allows you to display images that are optimized for different devices, without having to rely on JavaScript or CSS media queries.

Here’s an example of how you might use the <picture> tag:

<picture >
  < source srcset="large.jpg" media="(min-width: 800px)">
  < source srcset="small.jpg" media="(max-width: 799px)">
  < img src="small.jpg" alt="A picture">
</ picture >

In this example, the < source > elements define different sources for the image, based on the screen size of the user’s device. If the screen is at least 800 pixels wide, the browser will choose the large.jpg image, while if the screen is smaller than 800 pixels, it will choose the small.jpg image. The <img> element is used as a fallback for browsers that do not support the <picture> element.

hope you understand the basic concepts and use of Picture Tag in HTML

Source: AO Interaction Channel

Categories
Learning

What is the life cycle of an HTML request

Hello, Welcome

The life cycle of an HTML request can be divided into following stages:

  1. Request initiation: The request is initiated by the browser, usually in response to a user action, such as clicking a link, submitting a form, or refreshing the page.
  2. DNS Lookup: The browser checks the local cache and DNS servers to resolve the domain name to an IP address. If the domain name has not been resolved before, the browser will initiate a DNS lookup to obtain the IP address of the server.
  3. TCP Connection: The browser establishes a TCP connection with the server. This is the underlying communication channel that will be used to send the HTTP request and receive the response.
  4. Request sent: The browser sends an HTTP request to the server. The request includes information about the type of operation being performed (e.g., GET, POST, PUT, DELETE), the URL being requested, and any additional data that may be required (e.g., form data).
  5. Server processing: The server receives the request and processes it. This may involve retrieving data from a database, processing data, or generating a response.
  6. Response sent: The server generates an HTTP response and sends it back to the browser. The response includes information about the status of the request, the type of data being returned, and the actual data itself.
  7. Response received: The browser receives the response and processes it. This may involve updating the contents of the page, displaying an error message, or redirecting to another page.
  8. Resource loading: If the response includes references to additional resources (e.g., images, stylesheets, scripts), the browser will initiate separate requests for each of these resources.
  9. Page rendering: The browser uses the information in the response to render the final page.

This entire process can take place in a matter of milliseconds, allowing the user to interact with the web page in near-real-time.

Source: AI Interaction Channel

Happy learning!

Categories
Learning Tech

How to write basic Test case for React component using Jest or Enzyme

Lets quickly straight dive into it

import React from "react";
import { shallow } from "enzyme";
import TestComponent from "./TestComponent";

describe("TestComponent", () => {
  it("renders correctly", () => {
    const wrapper = shallow(<TestComponent />);
    expect(wrapper).toMatchSnapshot();
  });

  it("contains a button", () => {
    const wrapper = shallow(<TestComponent />);
    expect(wrapper.find("button").length).toEqual(1);
  });

  it("simulates click events", () => {
    const mockCallBack = jest.fn();
    const wrapper = shallow(<TestComponent handleClick={mockCallBack} />);
    wrapper.find("button").simulate("click");
    expect(mockCallBack.mock.calls.length).toEqual(1);
  });
});

In this example, the describe block creates a test suite for the TestComponent and the it blocks define individual test cases.

The shallow function from Enzyme is used to render a shallow version of the component.

The toMatchSnapshot assertion is used to check that the component is rendering correctly.

The find method is used to locate elements within the shallow render, and the simulate method is used to trigger events on those elements.

The jest.fn function is used to create a mock callback that can be passed as a prop to the component and tested.

Happy Learning.

Categories
Learning Tech

10 Key tips on preparing for ReactJS Interview

Hello,

Lets quickly go through the 10 keys, for preparing for React Js Interview

  1. React basics: Familiarize yourself with React concepts such as components, JSX, state, props, lifecycle methods, hooks, etc.
  2. React-Redux: Understand how to use Redux with React for state management.
  3. React Router: Learn how to handle routing in React applications.
  4. React performance optimization: Know how to optimize the performance of React applications, including techniques like lazy loading, memoization, and using shouldComponentUpdate.
  5. React hooks: Knowledge of React hooks and how they can be used in place of class components.
  6. React testing: Understand how to test React components using tools like Jest and Enzyme.
  7. Familiarity with CSS: Good understanding of CSS, including CSS-in-JS solutions like styled-components.
  8. JavaScript concepts: Good understanding of JavaScript concepts like closure, asynchronous programming, and ES6 syntax.
  9. Git: Knowledge of Git and how to use it for version control.
  10. Problem solving skills: Be prepared to solve algorithmic problems and explain your thought process.

Hope you enjoy learning!

Categories
Learning Tech

Very basic of How to create a React Fiber/React Js Project from scratch

Here is the basic process to create a project with React Fiber:

  1. Install Node.js and npm (Node Package Manager) if you don’t have them installed already.
  2. Use npm to create a new React project by running the following command in your terminal or command prompt:
    npx create-react-app my-app
  3. Navigate to the newly created project directory:
    cd my-app
  4. Start the development server by running:
    npm start
  5. The development server should now be running on http://localhost:3000 in your browser.
  6. You can now start building your React Fiber application by modifying the files in the src directory.
  7. When you’re ready to deploy your application, run the following command to create a production build:
    npm run build

This should give you a basic understanding of how to create a React Fiber project. If you’re new to React, it may be helpful to go through some introductory tutorials before diving into your project.

Happy Learning!

Categories
Blog Tech

How to generate Public & Private SSH Keys on Windows?

Hello, Lets Begin.

Open a Command Prompt/Terminal Window.

Important Alert!: Before going further, there is very important to know. If you have already generated a private/public key pair, don’t do it again!.

Where to find those keys or check if generated or not?

Okay, lets quickly see that step, Open Explorer window and type in address of explorer %userprofile%/.ssh it will open the window for you.

Typing %userprofile%/.ssh

Result of opening the above path. if you already have files will be listed otherwise it would be empty, so you can continue following reading next few steps to generate up the same.

.ssh list keys if already generated on your system or otherwise it list empty

Follow steps if no keys are available in the case.

Lets go back to our open Terminal Window/Command Prompt enter command:

ssh-keygen -b 4096

You are prompted to answer a few questions.

First is “Enter file in which to save the key” Press enter to use the default location.

The next question is “Enter passphrase.” This step is optional, but good to have for better security. Use whatever you like or skip, and then press enter.

Then confirm the passphrase or enter if none.

Once done new keys will be saved to same path under .ssh

For example: C:\your-username\.ssh\id_rsa.pub

Then you can use both the files to upload it under your hosting server to make a communication with your server through terminal window.

To make a connection to hosting server from terminal windows, that’s another topic we will cover them later in new post.

Hope this solves your finding.

Happy Learning

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Downloads & Free

Download Free Bharat (India) West Bengal State Map SVG format

Hello,

Download Bharat (India) West Bengal State Map (SVG format) for Laser Cut or to Print for your school or college projects.

West-Bengal
Categories
Downloads & Free

Download Free Bharat (India) Uttar Pradesh State Map SVG format

Hello,

Download Bharat (India) Uttar Pradesh State Map (SVG format) for Laser Cut or to Print for your school or college projects.

Uttar Pradesh
Categories
Downloads & Free

Download Free Bharat (India) Uttarakhand State Map SVG format

Hello,

Download Bharat (India) Uttarakhand State Map (SVG format) for Laser Cut or to Print for your school or college projects.

Uttarakhand