res.writeHead覆盖不起作用

Question

我正在尝试覆盖Node.js中的res.writeHead方法，尽管它会抛出错误。这是代码：

const http = require('http');
http.createServer((req, res) => {
    const _writeHead = res.writeHead;
    res.writeHead = (...a) => {
        console.log('res.writeHead called!');
        _writeHead(...a);
    };
    res.writeHead(200, {
        'Content-Type': 'text/plain'
    });
    res.end('Hello, world!');
}).listen(2020);

记录

res.writeHead called!，然后在客户端连接时获得TypeError: Cannot read property 'statusMessage' of undefined。为什么呢？

Answer 1

当您致电_writeHead时，this对象未引用res。它引用全局上下文，阻止Node.js正常运行。将const _writeHead = res.writeHead;更改为const _writeHead = res.writeHead.bind(res);。