MongoDB and Mongoose work out of the box with Bun. This guide assumes you've already installed MongoDB and are running it as background process/service on your development machine. Follow this guide for details.

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Once MongoDB is running, create a directory and initialize it with bun init.

mkdir mongoose-app
cd mongoose-app
bun init

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Then add Mongoose as a dependency.

bun add mongoose

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In schema.ts we'll declare and export a simple Animal model.

import * as mongoose from "mongoose";

const animalSchema = new mongoose.Schema(
  {
    title: { type: String, required: true },
    sound: { type: String, required: true },
  },
  {
    methods: {
      speak() {
        console.log(`${this.sound}!`);
      },
    },
  },
);

export type Animal = mongoose.InferSchemaType<typeof animalSchema>;
export const Animal = mongoose.model("Animal", animalSchema);

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Now from index.ts we can import Animal, connect to MongoDB, and add some data to our database.

import * as mongoose from "mongoose";
import { Animal } from "./schema";

// connect to database
await mongoose.connect("mongodb://127.0.0.1:27017/mongoose-app");

// create new Animal
const cow = new Animal({
  title: "Cow",
  sound: "Moo",
});
await cow.save(); // saves to the database

// read all Animals
const animals = await Animal.find();
animals[0].speak(); // logs "Moo!"

// disconnect
await mongoose.disconnect();

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Let's run this with bun run.

bun run index.ts

Moo!

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This is a simple introduction to using Mongoose with TypeScript and Bun. As you build your application, refer to the official MongoDB and Mongoose sites for complete documentation.