无法读取未定义的Node.js和Jade的属性“长度”

Question

I get the error above i just cant figure it out why? I saw this error before and probably its because variables dont match.

My routes .js file:

var express = require('express');
var router = express.Router();
var mongo = require('mongodb');
var db = require('monk')('localhost/nodeblog');

router.get('/add', function(req, res, next) {
  var categories = db.get('categories');

  categories.find({}, {}, function(err, categories){
    res.render('addpost', {
      'title': 'Add Post',
      'categories': categories
    });
  });
})

router.post('/add', function(req, res, next){
  //Get form values
  var title = req.body.title;
  var category = req.body.category;
  var body = req.body.body;
  var author = req.body.author;
  var date = new Date();

  if (req.hasOwnProperty('file')) {
    console.log('Uploading File...');

    //File info
    var mainImageOriginalName = req.files.mainimage.originalname;
    var mainImageName = req.files.mainimage.name;
    var mainImageMime = req.files.mainimage.mimetype;
    var mainImagePath = req.files.mainimage.path;
    var mainImageExt = req.files.mainimage.extension;
    var mainImageSize = req.files.mainimage.size;
  } else {
    //Set a Default Image
    var mainImageName = 'noimage.png';
  }

  //Form Validation
  req.checkBody('title', 'Title field is required').notEmpty();
  req.checkBody('body', 'Body field is required');

  //Check Errors
  var errors = req.validationErrors();

  if(errors){
    res.render('addpost', {
      'errors': errors,
      'title': title,
      'body': body
    });
  } else {
    var posts = db.get('post');

    //Submit to DB
    posts.insert({
      'title': title,
      'body': body,
      'category': category,
      'date': date,
      'author': author,
      'mainimage': mainImageName
    }, function(err, post){
      if(err){
        res.send('There was an issue submitting the post');
      } else {
        req.flash('succes', 'post submitted');
        res.location('/');
        res.redirect('/');
      }
    });
  }
});

module.exports = router;

My .jade file:

extends layout

block content
  h1=title
  ul.errors
    if error
      each error, i in errors
        li.alert.alert-danger #{error.msg}
  form(method='post', action='/posts/add', enctype='multipart/form-data')
    .form-group
      label Title:
      input.form-control(name='title', type='text')
    .form-group
      label Category
      select.form-control(name='category')
        each category, i in categories
          option(value='#{category.title}') #{category.title}
    .form-group
      label Body
      textarea.form-control(name='body', id='body')
    .form-group
      label Main Image:
      input.form-control(name='mainimage', type='file')
    .form-group
      label Author:
      select.form-control(name='author')
        option(value='Marko') Marko
        option(value='John Do') John Do
    input.btn.btn-default(name='submit', type='submit', value='Save')
    script(src='/ckeditor/ckeditor.js')
    script
      | CKEDITOR.replace('body');

And a the full error log:

TypeError: C:\projects\nodeblog\views\addpost.jade:16
    14|       label Category
    15|       select.form-control(name='category')
  > 16|         each category, i in categories
    17|           option(value='#{category.title}') #{category.title}
    18|     .form-group
    19|       label Body

Cannot read property 'length' of undefined
    at eval (eval at <anonymous> (C:\projects\nodeblog\node_modules\jade\lib\index.js:218:8), <anonymous>:204:31)
    at eval (eval at <anonymous> (C:\projects\nodeblog\node_modules\jade\lib\index.js:218:8), <anonymous>:241:4)
    at eval (eval at <anonymous> (C:\projects\nodeblog\node_modules\jade\lib\index.js:218:8), <anonymous>:374:22)
    at res (C:\projects\nodeblog\node_modules\jade\lib\index.js:219:38)
    at Object.exports.renderFile (C:\projects\nodeblog\node_modules\jade\lib\index.js:380:38)
    at Object.exports.renderFile (C:\projects\nodeblog\node_modules\jade\lib\index.js:370:21)
    at View.exports.__express [as engine] (C:\projects\nodeblog\node_modules\jade\lib\index.js:417:11)
    at View.render (C:\projects\nodeblog\node_modules\express\lib\view.js:126:8)
    at tryRender (C:\projects\nodeblog\node_modules\express\lib\application.js:639:10)
    at EventEmitter.render (C:\projects\nodeblog\node_modules\express\lib\application.js:591:3)
    at ServerResponse.render (C:\projects\nodeblog\node_modules\express\lib\response.js:961:7)
    at C:\projects\nodeblog\routes\posts.js:48:9
    at Layer.handle [as handle_request] (C:\projects\nodeblog\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\projects\nodeblog\node_modules\express\lib\router\route.js:131:13)
    at Route.dispatch (C:\projects\nodeblog\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (C:\projects\nodeblog\node_modules\express\lib\router\layer.js:95:5)

I would appreciated if someone helped.

Answer 1

Please console error object and check whether you are getting categories or not while fetching them in below code.

    router.get('/add', function(req, res, next) {
      var categories = db.get('categories');

      categories.find({}, {}, function(err, categories){
** console error and check categories type should be an array**
        res.render('addpost', {
          'title': 'Add Post',
          'categories': categories
        });
      });
    })