路由出问题了，请教老师

编译时报错如下：

 ERROR  Failed to compile with 1 error                                                                             21:47:17

 error  in ./src/router/index.js

Module not found: Error: Can't resolve 'vue-router' in 'D:\todolist\src\router'

ERROR in ./src/router/index.js 1:0-60

Module not found: Error: Can't resolve 'vue-router' in 'D:\todolist\src\router'

 @ ./src/main.js 3:0-30 5:30-36

webpack compiled with 1 error