javascript - Mongoose Express.js delete object with relationships -

so have schema town , want delete 1 town ads in , relashionships ads.here schemas:

let adschema = mongoose.schema ( {     author: {type: objectid, ref: 'user'},     category: {type: objectid, ref: 'category', required: true},     town: {type: objectid, ref: 'town', required: true}, } 

);

let categoryschema = mongoose.schema ( {     name: {type: string, required:true, unique: true},     ads: [{type: objectid, ref: 'ad'}] } 

);

let townschema = mongoose.schema ( {     name: {type: string, required:true, unique:true},     ads: [{type: objectid, ref: 'ad'}] } 

);

let userschema = mongoose.schema( {     email: {type: string, required: true, unique: true},     ads: [{type: objectid, ref: 'ad'}], } 

);

i using code this:

let id = req.params.id;     town.findbyidandremove(id).populate('ads').then(town => {         let ads = town.ads;         if (ads.length !== 0) {             ads.foreach(ad => {                 ad.findbyidandremove(ad.id).populate('author category').then(ad => {                     let author = ad.author;                     let category = ad.category;                     let authorindex = author.ads.indexof(ad.id);                     let categoryindex = category.ads.indexof(ad.id);                      category.ads.splice(categoryindex,1);                     category.save(err => {                         if (err) console.log(err);                     });                     author.ads.splice(authorindex, 1);                     author.save().then(() => {                         res.redirect('towns');                     })                 })             });         } else {             res.redirect('/');         }     }) 

actually working , deleted should throw me error(when trying delete town ads in it) in console , stuck on redirecting.this error:

(node:10200) unhandledpromiserejectionwarning: unhandled promise rejection (rejection id: 1): casterror: cast objectid failed value "towns" @ path "_id" model "town" (node:10200) deprecationwarning: unhandled promise rejections deprecated. in future, promise rejections not handled terminate node.js process non-zero exit code.

the problem in redirecting path.it should 1 in else scope:

            res.redirect('/');