Route get requires callback functions but got a object Undefined

Question

I am learning making Todo app  On the website  I am studying is https   coderwall com p 4gzjqw build-a-javascript-todo-app-with-express-jade-and-mongodb  I typed as instruction describes    app js  var main   require    routes main    var todo   require    routes todo    var todoRouter   express Router    app use   todos   todoRouter   app get      main index   todoRouter get     todo all   todoRouter post   create   todo create   todoRouter post   destroy  id   todo destroy   todoRouter post   edit  id   todo edit      routes todo js  module exports      all  function req  res       res send  All todos           viewOne  function req  res       console log  Viewing   req params id          create  function req  res       console log  Todo created           destroy  function req  res       console log  Todo deleted           edit  function req  res       console log  Todo   req params id   updated             and I got this error message     Error  Route get   requires callback functions but got a  object   Undefined    Did I miss something here

User · Answer

I got the same error  After debugging  I found that I misspelled the method name that I imported from the controller into the route file  Please check the method name

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I had the same error  The problem was in the export and import of the modules   Example of my solution   Controller  File  posts js   exports getPosts    req  res    gt        res json           posts                  tittle   First posts                   tittle   Second posts                            Router  File  posts js   const express   require  express    const   getPosts     require     controllers posts     const routerPosts   express Router    routerPosts get      getPosts    exports routerPosts   routerPosts    Main  File  app js   const express   require  express    const morgan   require  morgan    const dotenv   require  dotenv    const   routerPosts     require    routes posts     const app   express    const port   process env PORT    3000   dotenv config        Middleware app use morgan  dev      app use      routerPosts    app listen port       gt        console log  A NodeJS API is listining on port    port           Running the application  chrome output      20200409002022    http   localhost 3000        posts                  tittle    First posts                      tittle    Second posts                Console Log  jmendoza jmendoza-ThinkPad-T420   IdeaProjects NodeJS-API-Course Basic-Node-API  npm run dev   gt  node-api 1 0 0 dev  home jmendoza IdeaProjects NodeJS-API-Course Basic-Node-API  gt  nodemon app js   nodemon  2 0 3  nodemon  to restart at any time  enter  rs   nodemon  watching path s        nodemon  watching extensions  js mjs json  nodemon  starting  node app js  A NodeJS API is listining on port  3000 GET   304 5 093 ms - - GET   304 0 714 ms - - GET   304 0 653 ms - -  nodemon  restarting due to changes     nodemon  starting  node app js  A NodeJS API is listining on port  3000 GET   200 4 427 ms - 62 GET   304 0 783 ms - - GET   304 0 642 ms - -   Node Version  jmendoza jmendoza-ThinkPad-T420   IdeaProjects NodeJS-API-Course Node-API  node -v v13 12 0   NPM Version  jmendoza jmendoza-ThinkPad-T420   IdeaProjects NodeJS-API-Course Node-API  npm -v 6 14 4

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node js and express 4 use this sequences  express   require  express    var router   express Router     module exports   router    last line returns this type of error

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In the tutorial the todo all returns a callback object  This is required for the router get syntax   From the documentation      router METHOD path   callback       callback       The router METHOD   methods provide the routing functionality in   Express  where METHOD is one of the HTTP methods  such as GET  PUT    POST  and so on  in lowercase  Thus  the actual methods are   router get    router post    router put    and so on    You still need to define the array of callback objects in your todo files so you can access the proper callback object for your router   You can see from your tutorial that todo js contains the array of callback objects  this is what you are accessing when you write todo all    module exports         all  function req  res           res send  All todos              viewOne  function req  res           console log  Viewing     req params id              create  function req  res           console log  Todo created              destroy  function req  res           console log  Todo deleted              edit  function req  res           console log  Todo     req params id     updated

User · Answer

This thing also happened with my code  but somehow I solved my problem  I checked my routes folder  where my all endpoints are their   I would recommend you check your routes folder file and check whether you forgot to add your particular router link

User · Answer

My suggestion  if you are still using const XXX   require  library or path     when using module exports to export multiple functions use an ES6 arrow function for example  module exports        gt    const  getPosts    req  res     gt       res send  THIS WORKS        const getPost   async  req  res    gt         const   id     req params       try           const post   await PostMessage findById id                    res status 200  json post         catch  error            res status 404  json   message  error message                then Import  const getPosts   require     controllers posts js    Hope this helps    Cheers  www miyamotto net

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In my case I was trying to  get  from express app  Instead I had to do SET   app set  view engine   pug

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1  Make sure that you have imported the corresponding controller file in router file  2  Make sure that the function name written in the any of the router get   or router post   in router js file is exactly same as the function name written in the corresponding controller file  3  Make sure that you have written module exports router  at the bottom of router js file

User · Answer

There are two routes for get   app get      main index   todoRouter get     todo all     Error  Route get   requires callback functions but got a  object Undefined  This exception is thrown when route getdoes not get a callback function  As you have defined todo all in todo js file  but it is unable to find main index   That s why it works once you define main index file later on in the tutorial

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What happened to me is I was exporting a function like this   module exports        gt        const method   async  req  res    gt              return           method           but I was calling it like this   const main   require    module      instead  const main   require    module

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Make sure that  yourFile js   exports yourFunction   function a b       your code     matches  app js   var express   require  express    var app   express    var yourModule   require  yourFile    app get   your path   yourModule yourFunction     For me  I ran into this issue when copy pasting a module into another module for testing  needed to change the exports  xxxx at the top of the file

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Some time you miss below line  add this router will understand this   module exports   router

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check your closing tags in your model  it may be that you have defined a callback in another callback

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My problem was a mistake in importing  I imported my function into the router index js like below  const   index     require     controllers     and used it like this  router get      index index    This was my mistake  I must have used this  router get      index    So I changed it to the line above and my problem got solved

[node.js] Route.get() requires callback functions but got a "object Undefined"

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