AWS S3 Node.js example.

README.txt

Read up the docs on how to setup the cli. 
If you need to setup for pipeline or for production without the CLI, you would need to make some modification to the code. 
Blessings

index.ts

//Assuming this is your entry file
import express from "express";
//Other imports
import fileUpload from "express-fileupload";

export const app = express();

app.use(
    fileUpload({
        debug: true,
    }),
);
//Add other express middlewares, services and proxies

request_controller.ts

import { RequestHandler } from "express";
import { $S3 } from "s3/service/import/path";
export const uploadEcpDocumentController: RequestHandler = async (
    req,
    res,
    next,
) => {
  const file = req.files?.fileField; // Request would be multipart so it would be fileField would be name of the field.
  const key = 'someRandomStringToUseAsYourAWSKey';
  const document = await new $S3().uploadPrivateFile(file, key);
  //document is of the type ManagedUpload.SendData. Should read up that one.
  //Do whatever you would with the response. Normally format and return a response.
}

s3_service.ts

//This example is going to assume you've setup your /home/user/.aws/config /home/user/.aws/credential files well 
import { S3 } from "aws-sdk";

export class $S3 {
  _s3: S3 = new S3();
  
  async uploadPrivateFile(file?: UploadedFile, key?: string) {
        if (file) {
            const upload = await this._s3
                .upload({
                    Bucket: process.env.AWS_BUCKET || "",
                    Body: file.data,
                    Key: key || "",
                })
                .promise()
                .then((data) => {
                    return data;
                });

            return upload;
        } else {
            return null;
        }
    }
}