Fixing Mongoose Error: ISODate is not defined in Node.js

Updated: December 30, 2023 By: Guest Contributor Post a comment

Understanding the ISODate Error in Mongoose

When working with Mongoose, a popular Object-Data Modeling (ODM) library for MongoDB and Node.js, developers might encounter an error stating ISODate is not defined. This issue arises because ISODate is a MongoDB shell construct and not a recognized type in JavaScript or Node.js environments directly. Mongoose relies on JavaScript’s built-in Date object to handle dates and does not recognize the ISODate used in the MongoDB shell without additional configuration.

Resolving the Issue

To fix this error, replace any usage of ISODate with new Date() inside your Mongoose models or queries. The Date object is fully compatible with Mongoose and will store dates in the standard ISO format in MongoDB. In cases where you specifically require operations involving ISODate, such as seeding a database using shell scripts, the transformation should be done within the context of the MongoDB shell and not in the Mongoose context.

Additionally, you can create custom Mongoose schema types if you need to manipulate date values before saving. This allows you to use middleware to convert dates to the appropriate format for Mongoose and MongoDB.

Example of a Mongoose Schema Using Date

import mongoose from 'mongoose';

const { Schema } = mongoose;

const sampleSchema = new Schema({
  createdAt: {
    type: Date,
    default: () => new Date(),

const SampleModel = mongoose.model('Sample', sampleSchema);

export default SampleModel;

Handling Dates with Custom Mongoose Schema Types

If you have advanced date handling needs beyond what the Date type offers, you can define a custom schema type or utilize middleware. For instance, you can create middleware that processes your date fields before they are saved to the database.

import mongoose from 'mongoose';

const { Schema } = mongoose;

const dateMiddlewareSchema = new Schema({
  createdAt: Date

dateMiddlewareSchema.pre('save', function(next) {
  if (this.createdAt) {
    this.createdAt = new Date(this.createdAt);
  } else {
    this.createdAt = new Date();

const DateMiddlewareModel = mongoose.model('DateMiddleware', dateMiddlewareSchema);

export default DateMiddlewareModel;


In conclusion, when facing a ISODate is not defined error while using Mongoose, it’s important to remember that it stems from trying to use MongoDB-specific syntax where it isn’t applicable. Stick to JavaScript’s Date object, and if needed, extend functionality through Mongoose’s schema capabilities and middleware.