Mongoose Import for TypeScript Doesn't Work

Question

New to Node and Typescript. I am getting an error that mongoose.connect is not a function when I run tsc.

I have the following code:

import express = require('express');
import * as mongoose from "mongoose";

/** Routes for the app */
import apiUserRouter from "./api/user"

class App{

   public express :express.Application


    constructor() {
        this.express = express()
        this.setupDb();
    }

    private setupDb() : void {
        var mongoDb = 'mongodb://127.0.0.1/my_database';
        mongoose.connect(mongoDb);
        var db = mongoose.connection;
        db.on('error', console.error.bind(console, 'MongoDB Connection error'));
    }
}

If I change

import * as mongoose from "mongoose"

to

import mongoose = require('mongoose');

Then everything works fine.

I have run the following npm command for types as my understanding is that this should have fixed the issue.

npm install @types/mongoose --save

Edit: Adding my packages.json

{
    "name": "nodejs-ts-test2",
    "version": "1.0.0",
    "description": "",
    "main": "index.js",
    "scripts": {
        "test": "echo \"Error: no test specified\" && exit 1"
    },
    "author": "",
    "license": "ISC",
    "devDependencies": {
        "@types/express": "^4.11.1",
        "@types/mongoose": "^5.0.3",
        "typescript": "^2.7.2"
    },
    "dependencies": {
        "express": "^4.16.2",
        "mongoose": "^5.0.7"
    }
}

and tsconfig.json:

{
    "compilerOptions": {
        "target": "es2015",
        "module": "commonjs",
        "outDir": "dist",
        "strict": true,
        "noImplicitAny": false,
        "esModuleInterop": true,
        "allowSyntheticDefaultImports": true
    }
}

Akshar Patel · Accepted Answer · 2018-03-01 03:02:00Z

13

Since you didn't share your package.json or tsconfig, it was not possible to say where the error might be. So I created new project for the code you have shared such that the error does not occur. Compare the files that I am sharing with the ones you have to narrow down your problem.

The package.json

{
  "name": "mong_type",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@types/express": "^4.11.1",
    "@types/mongoose": "^5.0.3",
    "typescript": "^2.7.2"
  },
  "dependencies": {
    "express": "^4.16.2",
    "mongoose": "^5.0.7"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "target": "es2015",
    "module": "commonjs",
    "outDir": "./dist",
    "strict": true,
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true
  },
  "include": ["src"]
}

src/app.ts

import express from "express";
import mongoose from "mongoose";

class App {
  public express: express.Application;

  constructor() {
    this.express = express();
    this.setupDb();
  }

  private setupDb(): void {
    var mongoDb = "mongodb://127.0.0.1/my_database";
    mongoose.connect(mongoDb);
    var db = mongoose.connection;
    db.on("error", console.error.bind(console, "MongoDB Connection error"));
  }
}

edited Mar 1, 2018 at 3:02

answered Feb 27, 2018 at 6:32

Akshar Patel

5,8154 gold badges23 silver badges25 bronze badges

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4 Comments

Chuck Stapleton Over a year ago

Thank you for your help so far, it appears the express import now works. But the mongoose one still doesn't. When I run nodemon I get the following error: "mongoose.connect" is not a function.

Akshar Patel Over a year ago

Hey Chuck, Yeah sorry I didn't test that. I've updated the code to import mongoose so that you don't get that error.

Chuck Stapleton Over a year ago

Thank you for that. I will award the answer, however, why does 'import * as mongoose from "mongoose"' not work? It works on other pages I have in my project.

Akshar Patel Over a year ago

That's because I've used the rule "esModuleInterop": true in the tsconfig. If you remove that rule, you'll be able to import both express and mongoose using "import *" syntax.

Lucio Mollinedo · Accepted Answer · 2020-07-02 02:15:01Z

5

This:

import mongoose from 'mongoose'

worked for me after running:

npm install mongoose @types/mongoose --save

Way more detailed explanation on why this works, here.

answered Jul 2, 2020 at 2:15

Lucio Mollinedo

2,4341 gold badge36 silver badges32 bronze badges

1 Comment

Christopher Chase Over a year ago

FYI deprecated @types/[email protected]: Mongoose publishes its own types, so you do not need to install this package.

SuperUser Sudo · Accepted Answer · 2020-07-05 23:58:08Z

2

The solution to this problem is to comment the below line in your tsconfig.json file found in your project's base directory, just comment this damn line

"esModuleInterop":true

answered Jul 5, 2020 at 23:58

SuperUser Sudo

2952 silver badges7 bronze badges

Comments

kavi arasu · Accepted Answer · 2022-10-01 15:10:49Z

1

This issue got fixed for me after adding "moduleResolution":"Node" to the tsconfig.json

My tsconfig.json

{
    "compilerOptions": {
      "target": "es2015",                          
      "module": "es6",
      "checkJs":true,                                 
      "allowJs": true,
      "outDir": "build",                          
      "rootDir": "src",
      "strict": true,         
      "noImplicitAny": false,
      "esModuleInterop": true,
      "allowSyntheticDefaultImports": true,
      "moduleResolution":"Node"
    }
  }

edited Oct 1, 2022 at 15:10

answered Oct 1, 2022 at 15:09

kavi arasu

112 bronze badges

Comments

Redbeardjunior · Accepted Answer · 2022-10-25 20:42:35Z

0

I got it working,

Try

import express from 'express'
const app = express()
import mongoose from 'mongoose'

Its a mix up of code...

some prove of concept.

https://bobbyhadz.com/blog/javascript-to-load-es-module-set-type-module-in-package-json

answered Oct 25, 2022 at 20:42

Redbeardjunior

3172 silver badges18 bronze badges

Comments

C4pt4inC4nn4bis · Accepted Answer · 2023-01-08 16:54:15Z

Cannot get it working. esModuleInterop and allowSyntheticDefaultImports dont seem to change anything. It works with

const mongoose = require('mongoose');

but not with ES6 like this

import mongoose from 'mongoose'

or this

import * as mongoose from 'mongoose'

tsconfig.json

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "node",
    "importHelpers": true,
    "jsx": "preserve",
    "esModuleInterop": true,
    "resolveJsonModule": true,
    "sourceMap": true,
    "baseUrl": "./",
    "strict": true,
    "paths": {},
    "allowSyntheticDefaultImports": true,
    "skipLibCheck": true
  },
  "include": ["src"],
  "references": [
    { "path": "./tsconfig.node.json" }
  ]
}

{
  "name": "electron-vue-vite",
  "version": "2.0.0",
  "main": "dist-electron/main/index.js",
  "description": "Really simple Electron + Vue + Vite boilerplate.",
  "author": "草鞋没号 <[email protected]>",
  "license": "MIT",
  "private": true,
  "scripts": {
    "dev": "vite",
    "build": "vue-tsc --noEmit && vite build && electron-builder"
  },
  "engines": {
    "node": "^14.18.0 || >=16.0.0"
  },
  "devDependencies": {
    "@vitejs/plugin-vue": "^3.1.2",
    "@vue/devtools": "^6.4.5",
    "electron": "^22.0.0",
    "electron-builder": "^22.10.3",
    "typescript": "^4.8.4",
    "vite": "^3.2.2",
    "vite-plugin-electron": "^0.10.4",
    "vite-plugin-electron-renderer": "^0.11.3",
    "vue": "^3.2.40",
    "vue-router": "^4.1.6",
    "vue-tsc": "^1.0.9"
  },
  "debug": {
    "env": {
      "VITE_DEV_SERVER_URL": "http://127.0.0.1:3344"
    }
  },
  "keywords": [
    "electron",
    "rollup",
    "vite",
    "vue3",
    "vue"
  ],
  "dependencies": {
    "apollo-server-express": "^3.11.1",
    "element-plus": "^2.2.27",
    "express": "^4.18.2",
    "graphql": "^16.6.0",
    "mongodb": "^4.13.0",
    "mongoose": "^6.8.3"
  }
}

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