In a below Clock example, a new date state will be created with a constructor. You can use componentDidMount and componentWillUnmount with Class based React components. In applications with many components, it’s very important to free up resources taken by the components when they are destroyed. Component ) Lifecycle Methods with Classes Hello World class Message extends React. The constructor function is also where you honor the inheritance of the parent component by including the super() statement, which executes the parent component's constructor function, and your component has access to all the functions of the parent component. In React, component properties should be kept in an object called state. You can use it to initialize your component properties. Component Constructor - class based componentĬomponents constructor() function will be called when the component gets initiated. In general, you should initialize state in the constructor or use state object directly, and then call setState when you want to change it (if you are using class based components). For data that is going to change, we have to use state. props are set by the parent and they are fixed throughout the lifetime of a component. There are two types of data that control a component: props and state. You should learn all of them, but if you are starting a new project, you should use functions or consts to create a components.
First class based component are used, then functions and now const.
Stackblitz If you’re interested trying React, you can use an online code playgrounds. It saves the effort of recalculating the CSS style, layout for the page and rendering for the entire page. This selective rendering provides a major performance boost. So, React only render components that actually change in UI. React uses a virtual DOM (in-memory data structure cache) and computes the resulting differences to real DOM and then updates the browser's displayed DOM efficiently. React is only concerned with rendering data to the DOM, and that is why creating React applications usually requires the use of additional libraries, for example state management and routing.
It is maintained by Facebook and a community of individual developers and companies. It is specializes in helping developers build user interfaces to websites and web applications and mobile applications. It lets you compose complex UIs from small and isolated pieces of code called components. React is a declarative, efficient, and flexible JavaScript library for building user interfaces. Component Constructor - class based component