: CastError: Cast to ObjectId failed for value "" at path "_id" for model "Course" code example

Example 1: Cast to ObjectId failed for value

// it happens when you pass an invalid id to mongoose. 
// so first check it before proceeding, using mongoose isValid function

import mongoose from "mongoose";

// add this inside your route
if( !mongoose.Types.ObjectId.isValid(id) ) return false;

Example 2: Cast to ObjectId failed for value

import mongoose from "mongoose";

// add this inside your route
if( !mongoose.Types.ObjectId.isValid(id) ) return false;