mongoose $or with mixed string and _id (ObjectId) not working - node.js

Question

I am trying to make a method to fetch a "page" from the document base where the query matches _id or permalink.
The below code example returns a mongoose error:
'Cast to ObjectId failed for value "hello-world" at path "_id" for model "pages"'
Now, obviously the query isn't an ObjectId if the case is 'hello-world' or any other string permalink. So how do I go about using $or in this case, or is there a smarter way to go about it?
/**
* Describes methods to create, retrieve, update, and delete pages
* #returns void
*/
function Pages() {
this.pages = require('../models/pages')
this.users = require('../models/users')
require('mongoose').connect(require('../../config/database/mongodb').url)
}
/**
* Retrieve a page by permalink or id
* #param {string} pageQuery - id or permalink
* #callback {function} cFunction
*/
Pages.prototype.getOne = function(pageQuery, cFunction) {
this.pages.findOne({$or: [{ 'permalink': pageQuery }, { '_id': pageQuery }] })
.populate('author', 'email')
.select('title permalink body author')
.exec(function(error, result) {
if (error) {
cFunction(error)
return
}
cFunction(result)
})
}
Pages model
const mongoose = require('mongoose'),
Schema = mongoose.Schema,
ObjectId = Schema.ObjectId,
pages = new Schema({
title: { type: String },
permalink: { type: String, unique: true },
body: { type: String },
author: { type: ObjectId, ref: 'users' },
createdAt: { type: Date },
revisedAt: { type: Date }
})
.index({
title: 'text',
permalink: 'text',
body: 'text'
})
module.exports = mongoose.model('pages', pages)
Users model
const mongoose = require('mongoose'),
Schema = mongoose.Schema,
ObjectId = Schema.ObjectId,
users = new Schema({
email: { type: String, unique: true },
username: { type: String, unique: true },
password: { type: String },
createdAt: { type: Date }
})
.index({
email: 'text',
username: 'text'
})
module.exports = mongoose.model('users', users)

Answer 1

It looks like if you run new ObjectId(pageQuery) and it's not a valid ObjectId, it will throw an error telling you that (i.e. Error: Argument passed in must be a single String of 12 bytes or a string of 24 hex characters.)
In saying that, I would just use a try/catch block at the beginning of Pages.prototype.getOne to try and cast a pageQueryOid variable, and if you get to the catch block you know it's because pageQuery is not a valid ObjectId.
Using this method you no longer need an $or filter, but can just build your exact filter based on if pageQuery is a valid ObjectId. The following is just an example of what this might look like, but you can update it to meet your needs:
Pages.prototype.getOne = function(pageQuery, cFunction) {
var ObjectId = require('mongoose').Types.ObjectId
var pageQueryOid
try {
pageQueryOid = new ObjectId(pageQuery)
} catch(err) {
console.log("pageQuery is not a valid ObjectId...")
}
var filter
if (pageQueryOid) {
filter = { '_id': pageQueryOid }
} else {
filter = { 'permalink': pageQuery }
}
this.pages.findOne(filter)
.populate('author', 'email')
.select('title permalink body author')
.exec(function(error, result) {
if (error) {
cFunction(error)
return
}
cFunction(result)
})
}