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Purpose of formic is to remove the complexity of form handling in react and make form submission simpler.Formic uses yup to validate the form fields which is very simple to useFirst install the formic librarynpm install –save formicExampleimport React, { Component} from 'react'; import { Formik, FormikProps, Form, Field, ErrorMessage } from 'formik'; export class FormExample extends Component { handleSubmit = (values, { props = this.props, setSubmitting }) => { setSubmitting(false); return; } render() { return( ... Read More
The error boundary mechanism helps to show meaningful error message to user on production instead of showing any programming language error.Create a react class componentimport React, {Component} from 'react'; class ErrorBoundary extends Component{ state={ isErrorOccured:false, errorMessage:'' } componentDidCatch=(error, info)=>{ this.setState({isErrorOccured:true, errorMessage:error}); } render(){ if(this.state.isErrorOccured){ return Something went wrong }else{ return {this.props.children} } } } export default ErrorBoundary;We have a state object having two variables isErrorOccured and errorMessage which ... Read More
Understanding error messagesIf there is an error in code execution react displays a readable error message on screen with line number. We should understand the error message to correct it.We have a below file App.js having one input element. On change of input value we see the console text −import React, {Component} from 'react'; class App extends Component { onChangeHandler=(event)=>{ console.log(event.target.value); } render(){ return ( this.onChangeHandler(event)}/> ); } } export default ... Read More
LETS SEE HOW TO CREATE SIMPLE REACT FUNCTIONAL COMPONENTComponents are building blocks of React library. There are two types of components.Stateful componentStateless componentStateful component has a local state object which can be manipulated internally.Stateless component does not have a local state object but we can add some state using React hooks in it.CREATE A SIMPLE ES6 FUNCTIONconst player = () => { }Here we used a const keyword to function name so that it does not get modified accidentally. Let's add a return statement with some jsx code.const player = () => { return ( I'm ... Read More
Some basics of react routingReact-router is the main library and react-router-dom and react-router-native are the environment specific libraries. React-router-dom is used in browser based web applications generally. react-router-native is used in mobile based applications which can be developed using react-native.To install it use command npm install –save react-router-domThere are two types of router in case of web applications.BrowserRouterHashRouterThe difference between the two router types are visible in the way they formulate the URLs.e.g. https://hello.com/about => BrowserRoutere.g. http://hello.com/#/about => HashRouter (uses hash in it)BrowserRouter is more popular and it uses html5 history API to keep track of locations.HashRouter supports the legacy ... Read More
There are multiple ways to add bootstrap in react project.Using bootstrap CDNInstalling bootstrap dependencyUsing react bootstrap packagesUsing bootstrap CDNThis is the simplest way to add bootstrap. Like other CDN, we can add bootstrap CDN in index.html of the react project.Below is one of the react CDN urlIf we need the JavaScript components of bootstrap then we should add the jquery, popper.js in the index.htmlWith this the complete index.html will look like − React App hello Adding bootstrap dependencynpm install bootstrap ... Read More
Selenium Webdriver is a framework that allows automation testing. It allows testing across various browsers. It can execute multiple tests over multiple browsers on multiple OS. Web Driver makes it possible to write a test script in Linux and run it in Windows. There are multiple programming languages that are supported by Web Driver such as Java, Python, Ruby, .Net, PHP to create test scripts.Selenium Web driver is derived from −In Selenium2, integration of Web Driver was considered which was designed to address a few limitations of Selenium RC.Selenium was introduced with the following new features −It can test dynamic ... Read More
Given a binary tree, we have to print its leaf nodes and then we have to remove those leaf nodes and then repeat till there are no nodes left in the tree.ExampleSo the output of the problem should be −6 7 9 13 14 3 4 2 1ApproachWe have adopted an approach where we are applying DFS.For applying a temporary value zero is assigned to every value and then assign all the nodes with the value maximum(value of both child)+1.AlgorithmSTART STEP 1-> DEFINE A struct Node WITH DATA MEMBERS data, order, *left, *right STEP 2-> DEFINE A struct Node* ... Read More
Given a matrix mat[row][col] we have to print the given matrix in zig-zag fashion like in the given image below −So the output should be like −Output: 10 20 40 70 50 30 60 80 90For the above problem, we have followed a simple approach where we have to iterate the matrix diagonally and change the value of iteration to change the direction after every previous match.AlgorithmSTART STEP 1-> DECALRE AND SET k = 3, l = 3 STEP 2-> DECLARE A MATRIX mat[][3] STEP 3-> DECLARE AND SET row = 0, col = 0, flag = false; STEP 4-> ... Read More
We are given with a binary tree of distinct nodes and two nodes of the binary tree whose path in the binary tree we want to print.For Example − We want to print the path between node 140 to 211 so its output should be like −Output: 140->3->10->211The idea is to find paths form root nodes to the two nodes and store them in two separate vectors or arrays say path1 and path2.Now, there arise two different cases −If the two nodes are in different subtrees of root nodes − When the two nodes are in different subtrees like one ... Read More