What's Mongoose error Cast to ObjectId failed for value XXX at path "_id"?

Question

Mongoose's findById method casts the id parameter to the type of the model's _id field so that it can properly query for the matching doc. This is an ObjectId but "foo" is not a valid ObjectId so the cast fails.

This doesn't happen with 41224d776a326fb40f000001 because that string is a valid ObjectId.

One way to resolve this is to add a check prior to your findById call to see if id is a valid ObjectId or not like so:

if (id.match(/^[0-9a-fA-F]{24}$/)) {
  // Yes, it's a valid ObjectId, proceed with `findById` call.
}

Use existing functions for checking ObjectID.

var mongoose = require('mongoose');
mongoose.Types.ObjectId.isValid('your id here');

I had to move my routes on top of other routes that are catching the route parameters:

// require express and express router

const express = require("express");
const router = express.Router();

// move this `/post/like` route on top

router.put("/post/like", requireSignin, like);

// keep the route with route parameter `/:postId` below regular routes

router.get("/post/:postId", singlePost);

I have the same issue I add
_id: String .in schema then it start work

Are you parsing that string as ObjectId?

Here in my application, what I do is:

ObjectId.fromString( myObjectIdString );