I'm trying to upload an image from my form using Multer, when I insert the image everything works fine But when there is no image chosen I got an error.

• Here is multer config all uploaded images are stored in public/images/uploads:

//handle file upload

var storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, 'public/images/uploads/')
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now()+ '.jpg')
  }
});
var upload = multer({ storage: storage })

Now I want to get back the value of mainImageName but when I don't insert any image an error occurs cannot get property filename of undefined.

• Here is the rest :

  //Submit new post
  router.post('/add', upload.single('mainimage'), function(req, res, next) {
  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.file && req.file.mainimage){
  
      var mainImageName = req.file.filename;
      var mainImageMime = req.file.mainimage.mimetype;
      var mainImagePath = req.file.mainimage.path;
      var mainImageSize = req.file.mainimage.size;
  
  }else{
  
      //if there was no image uploaded!!
      //noimage.png should be placed in public/images/uploads
      mainImageName = 'noimage.png';
  }
  
  console.log(mainImageName); //always returns noimage.png !!
  
  //form validation
  req.checkBody('title', 'You forgot the title').notEmpty();
  req.checkBody('body', 'Please fill in the body').notEmpty();
  
  //check errors
  var errors = req.validationErrors();
  
  if(errors){
  

  var mycategories = []; var categories = db.get('categories'); categories.find({}, {}, function(err, categories) {

      for (i=0; i<categories.length; i++) {
            mycategories[i] = categories[i];
          }
   });
  res.render('addpost', {
          'pageTitle': 'Add Post',
          'errors': errors,
          'title': title,
          'body': body,
          'categories': mycategories
  
      });
  
  } else{
          var posts = db.get('posts');
          //submit Post
          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('success_msg', 'Post Submitted');
              res.location('/');
              res.redirect('/');
           }
           });
  }
  

  });