Middleware of express framework in nodejs and analysis of app.use and app.get methods-JS Tutorial-php.cn

Middleware of express framework in nodejs and analysis of app.use and app.get methods

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Release： 2018-09-07 17:30:36

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The content of this article is about the middleware of express framework in nodejs and the analysis of app.use and app.get methods. It has certain reference value. Friends in need can refer to it. I hope it will be useful to you. Helps.

Use node to develop projects. Express is a commonly used framework. The following introduces the core usage middleware and the use and get methods of the app:

The implementation of middleware is very simple:

// 一个简单的中间件
function middleware(req, res, next){
    // req 参数可以接受一些请求的参数(req.query/req.body) 和 请求头信息
    // res 用于响应信息
    // 调用next()方法则进入下一个中间件
}

// 几种常见的调用方式
app.use(middleware);
app.use(&#39;/user&#39;,middleware); // 匹配部分路径
app.get(&#39;/login&#39;,middleware);

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Next are some uses of app.get/use:

app.get(path,function); // 接收两个参数 路径 和 一个回调函数
app.use(path,function/router); // 也是接收两个参数 路径和get的区别是第二个可以放回调函数或者router对象

//值得注意的是，path如果忽略，如:app.use(function/router);也是合法的写法，表示匹配所有的路径

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Regarding the writing of path and function, the following example:

// get 访问示例会匹配/app和其子集路径，如:http:127.0.0.1:3000/app 以及http:127.0.0.1:3000/app[/aa/bb...等等]都会匹配
app.get(&#39;/app&#39;,(req, res, next) => {
    //TODO SOMETHING...
});

//use 路由匹配和get方法一样
app.use(&#39;/app&#39;,(req, res, next) => {
    //TODO SOMETHING...
});

//另一种写法
app.use((req, res, next) => {
    //TODO SOMETHING...
});

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But we often see this kind of Writing method:

const session = require(&#39;express-session&#39;);

app.use(session({
    secret: &#39;test01&#39;,
    resave: false,
    saveUninitialized: false
}));

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In fact, the implementation behind it is also very simple. Just return a class (req, res, next) => {} function, for example:

// 实现思路
app.use(myFunction());

function myFunction(){
// 做一些处理
    return (req, res, next) => {
        next();
    }

}

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Related recommendations:

Example to explain the method of obtaining get and post values and session verification in express in nodejs

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