如何在Express中将值从app文件传递到路由文件

方法1：将路由封装为接收参数的函数 #

把路由文件改成导出一个可接收配置参数的函数，返回Router实例，这样就能在引入时传递需要的值：

// routes/test.js
const express = require("express");

// 导出接收配置的函数
module.exports = (config) => {
  const router = express.Router();

  router.use((req, res, next) => {
    console.log("Time:", Date.now());
    next();
  });

  router.post("/", (req, res) => {
    console.log(config.url); // 使用传入的url
    res.send("请求处理完成");
  });

  return router;
};

在app.js中引入路由时传入参数：

// app.js
const express = require("express");
const app = express();
const port = 3000;
const url = "https://example.com/v1";

// 调用路由函数并传入配置
const testRouter = require("./routes/test")({ url });

app.use(express.json());
// 挂载路由到指定路径
app.use("/test", testRouter);

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

方法2：使用app.locals挂载全局变量 #

Express的app.locals可存储应用级全局变量，所有路由都能通过req.app.locals访问：

// app.js
const express = require("express");
const app = express();
const port = 3000;
const url = "https://example.com/v1";

// 将url挂载到app.locals
app.locals.apiBaseUrl = url;

const test = require("./routes/test");

app.use(express.json());
app.use("/test", test);

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

路由文件中通过req.app.locals获取值：

// routes/test.js
const express = require("express");
const router = express.Router();

router.use((req, res, next) => {
  console.log("Time:", Date.now());
  next();
});

router.post("/", (req, res) => {
  console.log(req.app.locals.apiBaseUrl); // 访问全局变量
  res.send("请求处理完成");
});

module.exports = router;

方法3：用自定义中间件注入值 #

如果只需要给特定路由传递值，可以写一个中间件把值注入到req对象：

// app.js
const express = require("express");
const app = express();
const port = 3000;
const url = "https://example.com/v1";
const test = require("./routes/test");

app.use(express.json());

// 自定义中间件，将url注入到req对象
app.use("/test", (req, res, next) => {
  req.apiUrl = url;
  next();
});

app.use("/test", test);

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

路由文件中直接从req获取注入的值：

// routes/test.js
const express = require("express");
const router = express.Router();

router.use((req, res, next) => {
  console.log("Time:", Date.now());
  next();
});

router.post("/", (req, res) => {
  console.log(req.apiUrl); // 使用注入的值
  res.send("请求处理完成");
});

module.exports = router;

内容的提问来源于stack exchange，提问作者Ahmedtijani Umar