React, as a popular JavaScript library for building user interfaces, employs a sophisticated rendering process to efficiently update the UI in response to changes in state or props. In this article, we'll delve into the render process in React, exploring its intricacies and significance in building dynamic and interactive web applications. We'll also provide ample code examples to illustrate key concepts. What is the Render Process? In React, the render process is the mechanism by which React determines what needs to be displayed on the screen based on changes in state or props. When a component's state or props change, React triggers a re-render, during which it updates the virtual DOM to reflect the new state of the application. The render process is at the core of React's declarative programming model, where developers describe what the UI should look like based on the current state, rather than imperatively manipulating the DOM. Example Scenario Let's consider a simple example to understand how the render process works. Suppose we have a React component that displays a counter: import React, { useState } from 'react'; const Counter = () => { const [count, setCount] = useState(0); const increment = () => { setCount(count + 1); }; return ( <div> <h1>Counter</h1> <p>Count: {count}</p> <button onClick={increment}>Increment</button> </div> ); }; export default Counter; In this example, the useState hook is used to define a state variable count, which tracks the current count value. When the "Increment" button is clicked, the increment function is called to update the count state, triggering a re-render of the component. The…

React, being a prominent library for building user interfaces in JavaScript, employs a complex internal process to manage updates efficiently. One significant phase in this process is known as "beginWork," where React begins the process of reconciling changes to the virtual DOM. In this article, we'll delve into the beginWork process in React, exploring its significance and how it shapes our applications, with ample code examples to illustrate key concepts. What is the Begin Work Process? In React's reconciliation process, the "beginWork" phase is the initial step. During this phase, React starts the process of reconciling changes to the virtual DOM by traversing the component tree and determining what updates need to be made. It begins by examining the root component and recursively traverses its children, comparing the previous and current states to identify changes. Example Scenario Let's consider a simple example to understand how the beginWork process operates. Suppose we have a React component that renders a counter: import React, { useState } from 'react'; const Counter = () => { const [count, setCount] = useState(0); const increment = () => { setCount(prevCount => prevCount + 1); }; return ( <div> <h1>Counter</h1> <p>Count: {count}</p> <button onClick={increment}>Increment</button> </div> ); }; export default Counter; In this example, the component maintains a count state using the useState hook. When the "Increment" button is clicked, the count is incremented by 1. The Begin Work Process in Action During the beginWork phase, React traverses the component tree and begins the process of reconciling changes. In our example, when the "Increment" button is clicked and…

React, being a powerful and widely-used JavaScript library for building user interfaces, employs a sophisticated internal mechanism to manage updates. One crucial phase in this process is known as "completeWork," where React finalizes the changes to the virtual DOM and applies them to the actual DOM. In this article, we'll delve into the completeWork process in React, exploring its significance and how it shapes our applications, with ample code examples to illustrate key concepts. What is the Complete Work Process? In React's reconciliation process, the "completeWork" phase is the final step. After React performs the diffing algorithm to identify the changes required to update the virtual DOM, it enters the "completeWork" phase. During this phase, React applies these changes to the actual DOM, ensuring that it accurately reflects the current state of the application. Example Scenario Let's consider a simple example to understand how the completeWork process operates. Suppose we have a React component that renders a list of items fetched from an API: import React, { useState, useEffect } from 'react'; const ItemList = () => { const [items, setItems] = useState([]); useEffect(() => { fetchItems(); }, []); const fetchItems = async () => { const response = await fetch('https://api.example.com/items'); const data = await response.json(); setItems(data); }; return ( <div> <h1>Item List</h1> <ul> {items.map(item => ( <li key={item.id}>{item.name}</li> ))} </ul> </div> ); }; export default ItemList; In this example, the useEffect hook fetches items from an API when the component mounts. Once the items are fetched, React updates the virtual DOM with the new data. The Complete Work Process…

In the world of React, understanding the various phases of its reconciliation process is crucial for mastering its intricacies. One of these phases, the commit phase, plays a significant role in updating the DOM and finalizing the changes made during the reconciliation process. In this article, we'll delve into the commit phase in React and explore its significance through illustrative examples. What is the Commit Phase? The commit phase in React occurs after the reconciliation phase, during which React updates the virtual DOM and determines which changes need to be applied to the actual DOM. Once the reconciliation process is complete, React enters the commit phase, where it applies the changes to the DOM and performs any side effects, such as updating refs or firing lifecycle methods. Example Scenario Let's consider a simple example to illustrate the commit phase in action. Suppose we have a React component that toggles the visibility of a div element when a button is clicked: import React, { useState } from 'react'; const ToggleComponent = () => { const [visible, setVisible] = useState(false); const toggleVisibility = () => { setVisible(!visible); }; return ( <div> <button onClick={toggleVisibility}>Toggle Visibility</button> {visible && <div>This div is now visible!</div>} </div> ); }; export default ToggleComponent; In this example, when the button is clicked, the toggleVisibility function is called, which toggles the value of the visible state. Depending on the value of visible, the inner div is either rendered or removed from the DOM. The Commit Phase in Action During the commit phase, React applies the changes to the DOM that…

React is a widely-used JavaScript library for building user interfaces. It's known for its simplicity, efficiency, and flexibility, making it a top choice for developers worldwide. In this article, we'll dive into some common knowledge points in React that every developer should be familiar with. Components and Props At the core of React development are components, which are reusable building blocks for UI elements. Components can be either functional or class-based. Let's take a look at examples of both: // Functional Component const FunctionalComponent = (props) => { return <div>{props.message}</div>; }; // Class Component class ClassComponent extends React.Component { render() { return <div>{this.props.message}</div>; } } Props, short for properties, are inputs to components that allow them to receive data from their parent component. Here's how you can pass props to components: <FunctionalComponent message="Hello, Functional Component!" /> <ClassComponent message="Hello, Class Component!" /> State and Lifecycle State is another fundamental concept in React, representing the internal data of a component. Unlike props, state is mutable and can be updated using the setState method. Stateful components manage their state internally, while stateless components rely on props for data. Lifecycle methods are special methods that are invoked at specific points in a component's lifecycle, such as when it is mounted, updated, or unmounted. They allow developers to perform tasks like fetching data, subscribing to events, or cleaning up resources. Common lifecycle methods include componentDidMount, componentDidUpdate, and componentWillUnmount. Hooks Introduced in React 16.8, hooks are functions that allow functional components to use state and other React features without writing a class. useState is a hook…

introduction snapshot is translated as a snapshot, which is used to directly obtain the status of the page at a certain runtime. The snapshot before and after the operation is stored, so that the page state can be redone and undone easily. this article mainly introduces the principle of snapshot tool implementation and its use in the project. Design to implement the history, redo and undo of page state, you need to support the following properties and methods Properties History: stores the history of the page state, including the page initialization state to the previous page state undo record: stores each redone operation record, which is used to recover after undo current record: temporarily stores the current page state, which is mainly used to store it in the history after the next operation Last time to insert data: the insertion interval is too small and additional processing is required  // History  recordList: string[] = []  ​  // cancel the record, which is used to redo  redoList: string[] = []  ​  // the current record is temporarily stored in the currentRecord variable, and then stored in recordList when the user modifies it.  currentRecord = ''  ​  // time when the data was last inserted  time = 0 method Storage history push when the user acts, the history is updated. The following points need to be considered. when the current operation time is less than 100 ms from the last insertion time, the current record is replaced and the add is canceled if the current record has a value, the last operation…

oninput and onchange of DOM oninput when entering content, it is called continuously, and the value can be taken continuously through element.value . Losing focus and getting focus will not be called. onchange is not called during input, but only when the value when losing focus and losing focus is inconsistent with value when gaining focus (the input changes). if you need to detect whether the contents of one of the user's input boxes have changed, onchange can handle this situation very well. <body> <input type="text" id="myInput" oninput="myinput()" /> <input type="text" id="change" onchange="mychange()" /> </body> <script> function myinput() { var x = document.getElementById("myInput").value; console.info("input", x); } function mychange() { var x = document.getElementById("change").value; console.info("change", x); } </script> onInput and onChange in React There is not much difference between onInput of React and onChange . It is triggered when the user continues to type, not when the user loses access or focus. to get focus related events, you need to use onFocus and onBlur . If you need to check whether the content entered by the user has changed, you need to compare the values manually, which is not as convenient as the native onChange . export default function InputChange() { function input(e) { console.info("input", e.target.value); } function change(e) { console.info("change", e.target.value); } return ( <div style={{ display: "flex", flexDirection: "column" }}> <input onFocus onBlur onInput={input}></input> <input onChange={change}></input> </div> ); } check the TypeScript type of the corresponding parameter: <input onInput={(evt: React.FormEvent<HTMLInputElement>) => {}}></input> <input onChange={(evt: React.ChangeEvent<HTMLInputElement>) => {}}></input> The argument to onInput is React.FormEvent , while onChange is React.ChangeEvent ,…

In many teams that fully use Hooks , the only scenario that uses ClassComponent is using ClassComponent to create ErrorBoundary . it can be said that if there are two lifecycle functions substitutes for Hooks , then ClassComponent can be completely discarded: getDerivedStateFromError componentDidCatch then why is there no Hook alignment yet? Today we talk about how these two lifecycle functions are implemented and the cost of porting them to Hook . ErrorBoundary implementation principle ErrorBoundary can catch errors in the React workflow in descendant components. React workflow refers to render phase, that is, component render , Diff algorithm occurs commit phase, that is, rendering DOM , componentDidMount/Update execution phase this is why errors that occur in event callbacks cannot be caught by ErrorBoundary -event callbacks are not part of the React workflow . how to catch errors The overall execution flow of render phase is as follows: do { try { // the specific execution process of render phase workLoop(); break; } catch (thrownValue) { handleError(root, thrownValue); } } while (true); you can find that if an error occurs in the render phase , the handleError method is captured and executed. similarly, the overall execution flow of commit phase is as follows: try { //... Specific implementation process } catch (error) { captureCommitPhaseError(current, nearestMountedAncestor, error); } if an error occurs in the commit phase , the captureCommitPhaseError method is captured and executed. getDerivedStateFromError principle how to deal with captured errors? We know that the first parameter of this.setState in ClassComponent can receive not only the new state , but…

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