In es6, "export default" is used to export real-time bound functions, objects or primitive values from the module. A file can only write an "export default" at the end to specify the default output for the module. Syntax is "export default function () {...}".
The operating environment of this tutorial: Windows 10 system, ECMAScript version 6.0, Dell G3 computer.
How to use export default in es6
The export statement is used to export real-time bound functions, objects or primitive values from the module so that other programs can import {foo, bar} from ' ./util/index' reference
There are two ways to export exports:
Named export export function FunctionName(){...} (each module contains any number)
Default export export default expression; (each module contains one)
export
You can write multiple exports in one file
Export in file a.js
export let name1 = '张三'; // 或者使用 var, const export function FunctionName(){...} export class ClassName {...}
Import in file b.js
import {name1,FunctionName,ClassName} from '../a.js';
Note that the following writing method will report an error:
// 报错 export 1; // 报错 var m = 1; export m; // 报错 function f() {} export f;
export default
A file can only have one export at the end default
Export externally in file a.js
const str = "export default的内容"; function FunctionName(){...} class ClassName {...} export default {str,FunctionName,ClassName}
In file b Import in .js
import name from '../a.js'; // 使用 console.log(name.str) name.FunctionName();
The difference between export and export default
1. Both export and export default can be used to export constants, functions, files, Modules, etc.
2. In a file or module, there can be multiple exports. The export default only has one at the end of the file.
3. When exporting through export, add { }, export default is not required, and can be given any name
Detailed introduction
We know that export default{} is indispensable when learning VUE. But its meaning must be understood.
export default{}This is used when reusing components. Suppose we write a single page component file A and need to use it in another file B, then we need to use the ES6 import/export syntax to define the output interface export in file A and introduce import in file B. Use the imported components so that you can reuse component A to match file B to generate html pages.
When using the import command, the user needs to know the name of the variable or function to be loaded, otherwise it cannot be loaded. However, users definitely want to get started quickly, and may not be willing to read the documentation to understand what attributes and methods the module has. In order to provide convenience to users and allow them to load modules without reading the documentation, the export default command is used to specify the default output for the module.
1. Basic usage
//export-default.js 这是一个模块文件export-default.js,它的默认输出是一个函数 export default function () { console.log('foo'); }
//import-default.js import customName from './export-default'; customName(); //'foo' //这是的import命令,可以用任意名称指向export-default.js输出的方法,这时就不需要知道原模块输出的函数名。 // 需要注意的是,这时import命令后面,不使用大括号。
When other modules load the anonymous module, the import command can specify any name for the anonymous function.
2. The export default command is used before non-anonymous functions
// export-default.js export default function foo() { console.log('foo'); } // 或者写成 function foo() { console.log('foo'); } export default foo; //上面代码中,foo函数的函数名foo,在模块外部是无效的。加载的时候,视同匿名函数加载。
[Related recommendations: javascript video tutorial, web front-end]
The above is the detailed content of How to use export default in es6. For more information, please follow other related articles on the PHP Chinese website!

HTML and React can be seamlessly integrated through JSX to build an efficient user interface. 1) Embed HTML elements using JSX, 2) Optimize rendering performance using virtual DOM, 3) Manage and render HTML structures through componentization. This integration method is not only intuitive, but also improves application performance.

React efficiently renders data through state and props, and handles user events through the synthesis event system. 1) Use useState to manage state, such as the counter example. 2) Event processing is implemented by adding functions in JSX, such as button clicks. 3) The key attribute is required to render the list, such as the TodoList component. 4) For form processing, useState and e.preventDefault(), such as Form components.

React interacts with the server through HTTP requests to obtain, send, update and delete data. 1) User operation triggers events, 2) Initiate HTTP requests, 3) Process server responses, 4) Update component status and re-render.

React is a JavaScript library for building user interfaces that improves efficiency through component development and virtual DOM. 1. Components and JSX: Use JSX syntax to define components to enhance code intuitiveness and quality. 2. Virtual DOM and Rendering: Optimize rendering performance through virtual DOM and diff algorithms. 3. State management and Hooks: Hooks such as useState and useEffect simplify state management and side effects handling. 4. Example of usage: From basic forms to advanced global state management, use the ContextAPI. 5. Common errors and debugging: Avoid improper state management and component update problems, and use ReactDevTools to debug. 6. Performance optimization and optimality

Reactisafrontendlibrary,focusedonbuildinguserinterfaces.ItmanagesUIstateandupdatesefficientlyusingavirtualDOM,andinteractswithbackendservicesviaAPIsfordatahandling,butdoesnotprocessorstoredataitself.

React can be embedded in HTML to enhance or completely rewrite traditional HTML pages. 1) The basic steps to using React include adding a root div in HTML and rendering the React component via ReactDOM.render(). 2) More advanced applications include using useState to manage state and implement complex UI interactions such as counters and to-do lists. 3) Optimization and best practices include code segmentation, lazy loading and using React.memo and useMemo to improve performance. Through these methods, developers can leverage the power of React to build dynamic and responsive user interfaces.

React is a JavaScript library for building modern front-end applications. 1. It uses componentized and virtual DOM to optimize performance. 2. Components use JSX to define, state and attributes to manage data. 3. Hooks simplify life cycle management. 4. Use ContextAPI to manage global status. 5. Common errors require debugging status updates and life cycles. 6. Optimization techniques include Memoization, code splitting and virtual scrolling.

React's future will focus on the ultimate in component development, performance optimization and deep integration with other technology stacks. 1) React will further simplify the creation and management of components and promote the ultimate in component development. 2) Performance optimization will become the focus, especially in large applications. 3) React will be deeply integrated with technologies such as GraphQL and TypeScript to improve the development experience.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Dreamweaver Mac version
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

WebStorm Mac version
Useful JavaScript development tools