NodeJS general guide
This post is a collection of notes related to general overview and guides of Nodejs.
How to start a web server
Once you’ve installed Node, create a file named app.js with the following code:
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World\n');
});
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
});
To run the app execude node app.js. Once it’s done, you can visit http://localhost:3000 and will see a ‘Hello World’.
How to send/handle HTTP requests
The http module allows Node.js to transfer data over HTTP. The module is responsible for:
- Building web servers
- Sending client requests
- Giving responses back to clients
- Managing connections
- Holding HTTP constants (methods, status codes)
To include the HTTP module, use the require() method:
var http = require('http');
The following code will send a GET request to NASA’s API and print out the URL for the astronomy picture of the day as well as an explanation:
const https = require('https');
https.get('https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY', (resp) => {
let data = '';
// A chunk of data has been recieved.
resp.on('data', (chunk) => {
data += chunk;
});
// The whole response has been received. Print out the result.
resp.on('end', () => {
console.log(JSON.parse(data).explanation);
});
}).on("error", (err) => {
console.log("Error: " + err.message);
});
Other ways to make HTTP requests
Request
First install the package npm install request. Then a request can be made like this:
const request = require('request');
request('https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY', { json: true }, (err, res, body) => {
if (err) { return console.log(err); }
console.log(body.url);
console.log(body.explanation);
});
Axios
Axios is a Promise based HTTP client for the browser as well as node.js.
To install from npm execute npm install axios.
And to make a request:
const axios = require('axios');
axios.get('https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY')
.then(response => {
console.log(response.data.url);
console.log(response.data.explanation);
})
.catch(error => {
console.log(error);
});
Got
Got is another Promise based lightweight solution. Again, install as: npm install got.
And the code is:
const got = require('got');
got('https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY', { json: true }).then(response => {
console.log(response.body.url);
console.log(response.body.explanation);
}).catch(error => {
console.log(error.response.body);
});
How to debug a script
Debugging process can be started in nodejs by adding the --inspect flag:
node --inspect index.js
Once it’s done, you will receive the following message:
Debugger listening on ws://127.0.0.1:9229/5f063ae5-c5ea-4371-ad7a-325ac9b25493
For help, see: https://nodejs.org/en/docs/inspector
After that you can open Chrome DevTools > Dedicated DevTools for Nodejs (green icon) > any other tabs with similar debugging experience. No words, just amazing.
Source: https://nodejs.org/en/docs/guides/debugging-getting-started/
How to dockerize an existing Nodejs app
First you have to install either Docker Desktop for Windows (Microsoft Windows 10) or Docker toolbox.
Then create a Dockerfile with the following content:
FROM node:10
# Create app directory
WORKDIR /usr/src/app
# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./
RUN npm install
# If you are building your code for production
# RUN npm ci --only=production
# Bundle app source
COPY . .
EXPOSE 8080
CMD [ "node", "server.js" ]
server.js should be replaced with the file name you “node”.
.dockerignore file is useful to prevent your local modules and debug logs from being copied onto a Docker image:
node_modules
npm-debug.log
Run the docker and build an image using the docker images command:
docker build -t <your username>/node-web-app .
Once the image is built, you can see it in the list:
$ docker images
# Example
REPOSITORY TAG ID CREATED
node 10 1934b0b038d1 5 days ago
<your username>/node-web-app latest d64d3505b0d2 1 minute ago
Last but not least, run the image you previously built:
docker run -p 49160:8080 -d <your username>/node-web-app
The output of your app can be printed with:
# Get container ID
$ docker ps
# Print app output
$ docker logs <container id>
# Example
Running on http://localhost:8080
Source: https://nodejs.org/en/docs/guides/nodejs-docker-webapp/#creating-a-dockerfile.
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