错误
C:\Users\Yang\Desktop\blog\node_modules\express\lib\application.js:210 throw new TypeError('app.use() requires a middleware function') ^ TypeError: app.use() requires a middleware function at Function.use (C:\Users\Yang\Desktop\blog\node_modules\express\lib\application.js:210:11) at Object.<anonymous> (C:\Users\Yang\Desktop\blog\app.js:31:5) at Module._compile (node:internal/modules/cjs/loader:1108:14) at Object.Module._extensions..js (node:internal/modules/cjs/loader:1137:10) at Module.load (node:internal/modules/cjs/loader:973:32) at Function.Module._load (node:internal/modules/cjs/loader:813:14) at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:76:12) at node:internal/main/run_main_module:17:47
原因
原因是因为 没有导出 module
（完全大意了，没有闪）
在 router.js 结尾中加入
module.exports = router;
