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Articles on Trending Technologies
Technical articles with clear explanations and examples
Uneven sorting of array in JavaScript
ProblemWe are required to write a JavaScript function that takes in an array of numbers, arr, as the only argument. Our function should sort this array in such a way that after sorting, the elements should follow this pattern −arr[0] < arr[1] > arr[2] < arr[3]....For example, if the input to the function is −const arr = [1, 5, 1, 1, 6, 4];Then the output can (there can be more than one possible answer as well) be −const output = [2, 3, 1, 3, 1, 2];ExampleThe code for this will be −const arr = [1, 5, 1, 1, 6, 4]; ...
Read MoreValidate URL in ReactJS
In this article, we are going to see how to validate a URL (Uniform Resource Locator) in a React application.To validate a URL, we are going to install a third-party package of ‘validator’ which is used to validate the URL. Example of a valid and an invalid URL are as follows −Valid URL − https://www.tutorialspoint.com/Invalid URL − https://www.tutorialspointInstalling the modulenpm install validatorORyarn add validatorNpm is the node package manager which manages our React package but yarn is the more secure, faster and lightweight package manager.ExampleIn this example, we will build a React application which takes a URL input from the ...
Read MoreUsing onKeyPress event in ReactJS
In this article, we are going to see how to access the keycode which the user has pressed in a React applicationTo detect the keycode or the key which the user has pressed from his keyboard then React has a predefined onKeyPress event for this. Although it is not fired for all keys like ALT, CTRL, SHIFT, ESC but it can detect other keys properly.The order of event firing is −onKeyDown − Fired when the user is pressing the keyonKeyPress − Fired when the user has pressed the keyonKeyUp − Fired when the user releases the keyExampleIn this example, we will ...
Read MoreSuspense in ReactJS
In this article, we will learn how to show a loader while the component is being lazily loaded.When the components are lazily loaded, it requires a fallback to be shown to indicate that the component is being loaded in the DOM.SyntaxExampleIn this example, we will build a Routing application that lazily loads the component and displays a loader while the component is being loaded lazily.App.jsximport React, { Suspense, lazy } from 'react'; import { BrowserRouter as Router, Route } from 'react-router-dom'; import Loader from './Loader.js'; const Contact = lazy(() => import('./Contact')); const App = () => ( ...
Read MoreStrict Mode in ReactJS
In this article, we are going to see how to highlight potential problems that we might have in a React Application.React.StrictMode is a helper functionality provided by React which allows us to write better React codes. It provides visual feedback in the form of warnings if we don’t follow the React guidelines, but it works only in the development mode.Note: They are unsafe to use while using async await.Use-cases of Strict Mode −Identifying components with unsafe lifecyclesWarning about legacy string ref API usageWarning about deprecated findDOMNode usageDetecting unexpected side effectsDetecting legacy context APIWe can also bind React.StrictMode to work only ...
Read MoreReactJS – useRef hook
In this article, we are going to see how to create a reference to any DOM element in a functional component.This hook is used to access any DOM element in a component and it returns a mutable ref object which will be persisted as long as the component is placed in the DOM.If we pass a ref object to any DOM element, then the .current property to the corresponding DOM node elements will be added whenever the node changes.Syntaxconst refContainer = useRef(initialValue);ExampleIn this example, we will build a React application that passes the ref object to two input fields.When clicked ...
Read MoreReactJS – useLayoutEffect hook
In this article, we are going to see how to set up side-effects or HTTP requests in a functional component.This hook has the similar functioning like that of useEffect hooks but rather than being called out asynchronously, it has a synchronous effect. This hook is used to load the data in the DOM synchronously and also works in the same phase like that of useEffect hook.Note: Use useLayoutEffect hook only if useEffect hooks don't give the expected output.SyntaxuseLayoutEffect()ExampleIn this example, we will build a React application that displays and updates the name synchronously.App.jsximport React, { useLayoutEffect, useState } from 'react'; ...
Read MoreWhat is strrev() Function in C language?
An array of characters is called a string.DeclarationThe syntax for declaring an array is as follows −char stringname [size];For example − char string[50]; string of length 50 charactersInitializationUsing single character constant −char string[10] = { ‘H’, ‘e’, ‘l’, ‘l’, ‘o’ ,‘\0’}Using string constants −char string[10] = "Hello":;Accessing − There is a control string "%s" used for accessing the string till it encounters ‘\0’.The strrev( ) FunctionThis function is used for reversing a string.The reversed string is stored in the same string.SyntaxThe syntax for strrev() function is as follows −strrev (string)ExampleThe following program shows the usage of strrev() function.#include main ( ...
Read MoreCounting pairs with range sum in a limit in JavaScript
Range SumRange sum rangeSum(i, j) is defined as the sum of the elements in an array between indices i and j (i ≤ j), inclusive.ProblemWe are required to write a JavaScript function that takes in an array of Integers, arr, as the first argument and two numbers, upper and lower as the second and third element.Our function is supposed to return the number of range sums that lie between the range [upper, lower], (both inclusive).For example, if the input to the function is −const arr = [1, 4, 3]; const upper = 5; const lower = 2;Then the output should ...
Read MoreLongest path in 2-D that contains increasing sequence in JavaScript
Increasing SequenceA sequence of numbers in which each succeeding element is either greater or equal to the preceding element is an increasing sequence.For instance, 4, 6, 8, 9, 11, 14 is increasing sequence 3, 3, 3, 3, 3, 3, 3 is also an increasing sequenceProblem:We are required to write a JavaScript function that takes in a 2-D array of numbers, arr, as the only argument. Our function should find and return the length of that longest path in the array that contains only increasing numbers.For example, if the input to the function is −const arr = [ [4, 5, ...
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