Shulou(Shulou.com)06/02 Report--

This article mainly explains the difference between Koa and Express. The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn the difference between Koa and Express.

Introduction to Koa

A web development framework based on node, using co as the underlying running framework, using the characteristics of Generator to achieve "no callback" asynchronous processing

ES7

A smaller, more expressive, more robust cornerstone

Using async function and Koa to discard callback function to enhance error handling

Very small size, because no middleware is bundled

Organized and executed in a stack-like manner

High-level "syntax candy" is provided in the low-level middleware layer, which improves interoperability and robustness.

Express

The basic framework of Node, basic Connect middleware, encapsulates routing, view processing and other functions.

Linear logic, routing and middleware are perfectly integrated and clear

The disadvantage is that callback callback is uncombinable and the exception cannot be caught.

ES5

The execution flow of connect: the middleware model of connect is linear, that is, it executes down one by one.

Difference

The treatment of Handler

Express ordinary callback function, which completes all Http requests of the current process on the same thread; Koa uses Generator Function as the responder, co as the underlying running framework, and uses the Generator feature to achieve "collaborative response"

Routin

The routing of Express is self-integrated; the need of Koa introduces middleware Koa-router

Startup mode

Koa adopts new Koa () express and traditional functional form function.

Callback

Koa has no callback. Express has callback.

Http Request

Koa1 uses this to replace req and res of Express

Context

Koa adds a Context object to replace Express's Request and Response as the context object for the request. There are also req, res, socket and other objects natively provided by Node.

Life cycle

The life cycle of Express is uncertain: express executes asynchronous functions internally and cannot determine when it will be finished; Koa determines that koa is based on await/async and must wait for the front-end await to finish executing the next operation.

Asynchronous process

Express uses callback to handle ES5; Koa1 uses generator (ES6); Koa2 uses async/await (ES7)

Error handling

Express uses callback to catch exceptions, but deep-seated exceptions cannot be caught. Koa uses try catch to solve exception catching.

Middle ware

Koa2 middleware: 1, realized by async await, the order of middleware execution is the "onion ring" model. 2. The middleware connects with each other through the next function. When one middleware calls next (), it will hand over the control to the next middleware. Until the next middleware stops executing next (), it will return along the way and hand over the control to the previous middleware. Express middleware: 1. Execute one after another sequentially, and the response response is written in the last middleware. 2. Features: a.app.use is used to register middleware; b. When encountering http request, judge which middleware is triggered according to path and method; c. Implement the next mechanism, that is, the previous middleware will trigger the next middleware through next

Thank you for your reading, the above is the content of "the difference between Koa and Express", after the study of this article, I believe you have a deeper understanding of the difference between Koa and Express, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.