Having modules problems Dockerizng simple node app - node.js

Question

Having some problems while trying to create my first node.js app , super new to JS..
Trying to dockerize the app , like so :
docker build -t echo_app .
docker run -p 3000:3000 echo_app
End goal is to echo user input , like so :
http://example/?name=Eyal -> Hello Eyal
http://example/ -> Hello World
ERROR IM GETTING
Error: Cannot find module 'express'
Require stack:
- /app/index.js
.
.
code: 'MODULE_NOT_FOUND',
requireStack: [ '/app/index.js' ]
}
Directroy containes :
index.js
const express = require('express')
const log4js = require('log4js')
const app = express()
const logger = log4js.getLogger()
const echo = (req, res) => {
logger.debug("Request: ", req)
const input = 'name' in req.query ? req.query.input : ''
if (input.length == 0) {
res.send('Echo World')
} else {
res.send(`Echo ${input}`)
}
}
app.get('/', (req, res) => echo(req, res))
Dockerfile
FROM mhart/alpine-node:12
WORKDIR /app
ADD . ./
ENTRYPOINT ["node", "/app/index.js"]
package.json
{
"name": "echo",
"version": "1.0.0",
"description": "You talk, we talk back!",
"main": "index.js",
"author": "eyal",
"license": "MIT",
"dependencies": {
"express": "^4.17.1",
"js-yaml": "^3.13.1",
"log4js": "^5.2.2",
"saslprep": "^1.0.3"
}
}

Answer 1

To get it up and running, you first need to install the node dependencies by adding npm install to your Dockerfile, like this
FROM mhart/alpine-node:12
WORKDIR /app
ADD . ./
RUN npm install
ENTRYPOINT ["node", "/app/index.js"]
Then you need to have your Node app listen for requests by adding
app.listen(3000, () => {
console.log(`Example app listening at http://localhost:3000`)
})
at the bottom of index.js.
Finally, a small error in your code. req.query.input needs to be req.query.name.
That should hopefully get you going.