Node.js/Express.js - 如何覆盖/拦截 res.render 函数? [英] Node.js / Express.js - How to override/intercept res.render function?

问题描述

我正在使用 Connect/Express.js 构建一个 Node.js 应用程序，我想拦截 res.render(view, option) 函数以在将其转发到原始渲染函数之前运行一些代码.

I'm building a Node.js app with Connect/Express.js and I want to intercept the res.render(view, option) function to run some code before forwarding it on to the original render function.

app.get('/someUrl', function(req, res) {

    res.render = function(view, options, callback) {
        view = 'testViews/' + view;
        res.prototype.render(view, options, callback);
    };

    res.render('index', { title: 'Hello world' });
});

它看起来像一个人为的例子，但它确实适合我正在构建的整体框架.

It looks like a contrived example, but it does fit in an overall framework I'm building.

我对 JavaScript 的 OOP 和原型继承的了解有点薄弱.我该怎么做这样的事情?

My knowledge of OOP and Prototypal inheritance on JavaScript is a bit weak. How would I do something like this?

更新:经过一些实验，我得出了以下结论:

Update: After some experimentation I came up with the following:

app.get('/someUrl', function(req, res) {

    var response = {};

    response.prototype = res;

    response.render = function(view, opts, fn, parent, sub){
        view = 'testViews/' + view;
        this.prototype.render(view, opts, fn, parent, sub);
    };

    response.render('index', { title: 'Hello world' });
});

似乎可以.不确定这是否是最佳解决方案，因为我正在为每个请求创建一个新的响应包装器对象，这会不会有问题?

It seems to work. Not sure if it's the best solution as I'm creating a new response wrapper object for each request, would that be a problem?

推荐答案

老问题，但发现自己也在问同样的问题.如何拦截res渲染?现在使用 express 4.0x 的东西.

Old question, but found myself asking the same thing. How to intercept res render? Using express 4.0x something now.

您可以使用/编写中间件.这个概念起初对我来说有点令人生畏，但经过一些阅读后，它变得更有意义了.只是对于其他阅读本文的人来说，覆盖 res.render 的动机是提供全局视图变量.我希望 session 在我的所有模板中都可用，而不必在每个 res 对象中输入它.

You can use/write middleware. The concept was a bit daunting to me at first, but after some reading it made a little more sense. And just for some context for anyone else reading this, the motivation for overriding res.render was to provide global view variables. I want session to be available in all my templates without me having to type it in every res object.

基本的中间件格式是.

app.use( function( req, res, next ) {
    //....
    next();
} );

下一个参数和函数调用对执行至关重要.next 是回调函数，允许多个中间件在不阻塞的情况下做他们的事情.要获得更好的解释，请阅读此处

The next param and function call are crucial to execution. next is the callback function, to allow multiple middleware to do their thing without blocking. For a better explanation read here

这可以用来覆盖渲染逻辑

This can then be used to override render logic

app.use( function( req, res, next ) {
    // grab reference of render
    var _render = res.render;
    // override logic
    res.render = function( view, options, fn ) {
        // do some custom logic
        _.extend( options, {session: true} );
        // continue with original render
        _render.call( this, view, options, fn );
    }
    next();
} );

我已经使用 express 3.0.6 测试了这段代码.它应该可以毫无问题地与 4.x 一起使用.您还可以使用

I've tested this code, using express 3.0.6. It should work with 4.x without issue. You can also override specific URLs combos with

app.use( '/myspcificurl', function( req, res, next ) {...} );

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