Use NestJs package in nodejs/express project

Question

I developed a nest JS module. I published that on npm using npm publish.

Now i would like to use that NestJS module in a project built on nodejs and express.

Please advise if I can use a nestjs Module in node/express project. If yes is there any documentation available on that.

As per comment from User adding few more details.

This is kind of Library which is having a module with few methods exported. These method contains implementation which calls aws sns service to send push notification.

I found a link now trying to use that.

https://codeburst.io/https-chidume-nnamdi-com-npm-module-in-typescript-12b3b22f0724

Thanks in advance.

This question is way too broad to answer in it's current state. What things does your module contain? Is it middleware, services, pipes, etc? Please be more clear about what your actual code does — Jesse Carter, Jan 25 '19 at 01:24

score 8 · Answer 1 · answered Jan 26 '19 at 00:02

Because a NestJS Module is itself a module for an express app, what you could do to make that module usable inside another app that is not using currently NestJS, is to mount it as a sub app.

I've build a NestJS module and mounted it as a subapp of a vanilla express app, you could borrow from my example test here: https://github.com/tzkmx/nestjs-graphql-as-express-subapp

The key is exporting your Module as a sub app already initialized, you could not mount the modue directly inside another express app without using the NestJS framework itself in it.

// src/sub-app/boot.js
import { NestFactory } from '@nestjs/core'
import { SubAppModule } from './module'

export default async function bootstrap () {
  const app = await NestFactory.create(SubAppModule)

  return app
}

// src/app.js
import bootstrapSubApp from './sub-app/boot'
import express from 'express'

const app = express()

app.get('/', (req, res) => res.send('hello express\n'))

async function mountSubApp (app, mountPath, subAppBoot) {
  const subApp = await subAppBoot()
  await subApp.init()

  app.use(mountPath, subApp.getHttpAdapter().getInstance())
  return app
}

mountSubApp(app, '/sub', bootstrapSubApp)
.then(app => app.listen(4000))

As you can see, it is needed first call subApp.init() and then getting the express instance with subApp.getHttpAdapter().getInstance() to mount it in the vanilla js express app.

I didn't tried this. But what i did was exported methods inside main.ts/index.ts whatever file you have as your entry point , and i was able to call these methods by installing this package in another application. — user2587202, Jan 31 '19 at 07:29

score 0 · Answer 2 · answered Jan 31 '19 at 07:37

Just for Update.

I exported method inside main.ts/index.ts whichever file is your entry point.

After that i did

1: npm run build 2: npm publish.

After doing this when i installed published package inside another project of express/nest, i was able to call methods.

Thanks

Eylon · Answer 3 · 2021-05-27T09:56:18.590

You can use ExpressAdapter to host express application inside your nest.js application.

import { NestFactory } from '@nestjs/core'
import { SubAppModule } from './sub-app/module'
import {ExpressAdapter} from "@nestjs/core/adapters/express-adapter";
import {expressApp} from "./expressApp";

async function bootstrap () {
  const app = await NestFactory.create(SubAppModule, new ExpressAdapter(expressApp))
  app.listen(4444)
  return app
}

bootstrap()

you might see the full example based on @Jesús Franco original example: https://github.com/eylonmalin/nestjs-graphql-as-express-subapp

Use NestJs package in nodejs/express project

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