尝试在Node.js中提供png :无法读取未定义属性的“结束”

Question

我是一个节点，网页开发和编程初学者以下‘获得编程与Node.js’由乔纳森韦克斯勒。我已经完成了关于香草节点路由的部分的结尾部分，下面是main.js中的代码：

  http = require("http"),
  httpStatusCodes = require("http-status-codes"),
  fs = require("fs"); // This is a node js core module which interacts with the filesystem on behalf of the app.
(router = require("./router")),
  (plainTextContentType = {
    "Content-Type": "text/plain",
  }),
  (htmlContentType = {
    "Content-Type": "text/html",
  }),
  (pngContentType = {
    "Content-Type": "image/png",
  }),
  (customReadFile = (file, res) => {
    fs.readFile(`./${file}`, (errors, data) => {
      if (errors) {
        console.log("Error reading the file...");
      }
      res.end(data);
    });
  });

router.get("/", (req, res) => {
  res.writeHead(httpStatusCodes.OK, plainTextContentType);
  res.end("INDEX");
});

router.get("/index.html", (req, res) => {
  res.writeHead(httpStatusCodes.OK, htmlContentType);
  customReadFile("views/index.html", res);
});

router.get("/image.png", (req, res) => {
  res.writeHead(httpStatusCodes.OK, pngContentType);
  customReadFile("public/images/image.png");
});

router.post("/", (req, res) => {
  res.writeHead(httpStatusCodes.OK, plainTextContentType);
  res.end("POSTED");
});

http.createServer(router.handle).listen(3000);
console.log(`The server is listening on port number: ${port}`);

它可以很好地加载/index.html文件，但是当我尝试加载/image.png (存储在正确的文件夹中，public/images/image.png)时，它总是与错误消息TypeError:无法读取未定义的属性'end‘一起崩溃。

无论我使用什么图像，都会发生这种情况，如果我将图像移动到另一个文件夹(如视图)，也会发生这种情况。我还尝试编写res.write(数据)；res.end()，但也没有效果。我也尝试在fs.readFile中使用异步函数，但我不认为这是问题所在，因为如果我正确理解，fs.readFile本身应该在函数内同步执行。

编辑

router.js的代码，以防有帮助：

const httpStatus = require("http-status-codes"),
  htmlContentType = {
    "Content-Type": "text/html",
  },
  routes = {
    GET: {
      "/info": (req, res) => {
        res.writeHead(httpStatus.OK, {
          "Content-Type": "text/plain",
        });
        res.end("Welcome to the Info Page!");
      },
    },
    POST: {},
  };

exports.handle = (req, res) => {
  try {
    if (routes[req.method][req.url]) {
      routes[req.method][req.url](req, res);
    } else {
      res.writeHead(httpStatus.NOT_FOUND, htmlContentType);
      res.end("<h1>No such file exists</h1>");
    }
  } catch (ex) {
    console.log("error: " + ex);
  }
};

exports.get = (url, action) => {
  routes["GET"][url] = action;
};

exports.post = (url, action) => {
  routes["POST"][url] = action;
};

Answer 1

您必须将res对象作为第二个参数传递给您的customReadFile函数，以使其工作。你所拥有的：

router.get("/image.png", (req, res) => {
  res.writeHead(httpStatusCodes.OK, pngContentType);
  customReadFile("public/images/image.png"); // <-- 2nd arg missing
});

你想要的是：

router.get("/image.png", (req, res) => {
  res.writeHead(httpStatusCodes.OK, pngContentType);
  customReadFile("public/images/image.png", res); // <-- 2nd arg added
});