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This article will explain in detail the relationship between koa and node. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Koa is a web development framework based on Node.js platform, relying on "node v7.6.0" or ES2015 and later and async method support; Koa does not bundle any middleware, but provides an elegant method to help users write server-side applications quickly and happily.

This tutorial operating environment: windows7 system, nodejs version 12.19.0, DELL G3 computer.

Koa-- the next Generation web Development Framework based on Node.js platform

Koa is a new web framework built by the people behind Express to become a smaller, more expressive, and more robust cornerstone in the field of web applications and API development. By using the async function, Koa helps you discard the callback function and powerfully enhance error handling. Instead of bundling any middleware, Koa provides an elegant way to help you write server-side applications quickly and happily.

Koa was born to solve some design defects of Express. Its middleware can be written through async function, and await next () can interrupt the execution of the middleware until all subsequent middleware has been executed, and then implement the onion model through await next ().

Another feature is the simplified handling of request and response, both of which are mounted on ctx, and the returned content can also be used by direct assignment, such as: ctx.response.body = fs.createStream ('really_large.xml').

And Koa cut off the routing function, it is realized through middleware, which is a minimalist idea of the micro-kernel.

Core functions (documentation for Koa):

More extreme request / response simplification than Express, such as:

Ctx.status = 200

Ctx.body = 'hello node'

Middleware implemented using async function.

Have the ability to "suspend execution".

It also fits the onion model in the case of asynchronism.

Simplify the kernel, and all the additional functions are moved to the middleware.

Installation

Koa relies on node v7.6.0 or ES2015 and later and async method support.

You can use your favorite version manager to quickly install supported node versions:

$nvm install 7$ npm I koa$ node my-koa-app.js

Using Babel to implement Async method

To be in node

< 7.6 版本的 Koa 中使用 async 方法, 我们推荐使用 babel's require hook. require('babel-register');// 应用的其余 require 需要被放到 hook 后面const app = require('./app'); 要解析和编译 async 方法, 你至少应该有 transform-async-to-generator 或 transform-async-to-module-method 插件. 例如, 在你的 .babelrc 文件中, 你应该有: { "plugins": ["transform-async-to-generator"]} 你也可以用 env preset 的 target 参数 "node": "current" 替代. 应用程序 Koa 应用程序是一个包含一组中间件函数的对象，它是按照类似堆栈的方式组织和执行的。 Koa 类似于你可能遇到过的许多其他中间件系统，例如 Ruby 的 Rack ，Connect 等，然而，一个关键的设计点是在其低级中间件层中提供高级"语法糖"。 这提高了互操作性，稳健性，并使书写中间件更加愉快。 这包括诸如内容协商，缓存清理，代理支持和重定向等常见任务的方法。 尽管提供了相当多的有用的方法 Koa 仍保持了一个很小的体积，因为没有捆绑中间件。 必修的 hello world 应用: const Koa = require('koa');const app = new Koa();app.use(async ctx =>

{ctx.body = 'Hello World';}); app.listen (3000); this is the end of the article on "what is the relationship between koa and node". I hope the above content can be helpful to you so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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