Node.js Tips — Request URLs, Parsing Request Bodies, Upload

Like any kind of apps, there are difficult issues to solve when we write Node apps.

In this article, we’ll look at some solutions to common problems when writing Node apps.

Get Path from the Request

We can get the path from the request by using the request.url to get parse the request URL.

For instance, we can write:

const http = require("http");
const url = require("url");

const onRequest = (request, response) => {
  const pathname = url.parse(request.url).pathname;
  console.log(pathname);
  response.writeHead(200, { "Content-Type": "text/plain" });
  response.write("hello");
  response.end();
}

http.createServer(onRequest).listen(8888);

All we have to do is to get the request.url property to get the URL.

Then we can parse it with the url module.

We can then get the pathname to get the relative path.

Convert Relative Path to Absolute

We can convert a relative path to an absolute path by using the path module’s resolve method.

For example, we can write:

const resolve = require('path').resolve
const absPath = resolve('../../foo/bar.txt');

We call resolve with a relative path to return the absolute path of the file.

Get the String Length in Bytes

We can get the string length in bytes by using the Buffer.byteLength method.

For instance, we can write;

const byteLength = Buffer.byteLength(string, 'utf8');

We pass in a string to Buffer.byteLength to get the string length in bytes.

Get Data Passed from a Form in Express

To get data passed in from a form in Express, we can use the body-parser package to do that.

Then to get the parsed results, we can get it from the req.body property.

We can write:

const bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({ extended: true }));

app.post('/game', (req, res) => {
  res.render('game', { ...req.body });
});

We call app.post to create a POST route, which gets the request body via req.body because we called bodyParser.urlencoded to parse URL encoded payloads.

extended set to true lets the body-parser accept JSON like data within the form data including nested objects.

With this option, we don’t have to send key-value pairs as we do with traditional HTML form send.

Running Multiple Express Apps on the Same Port

We can use app.use to incorporate multiple Express apps and run them on the same port.

For instance, we can write:

app
  .use('/app1', require('./app1').app)
  .use('/app2', require('./app2').app)
  .listen(8080);

We require app1 and app2 to use the routes from both of them in one app.

Then we call listen to listen to requests in port 8080.

Change Working Directory with NodeJs child_process

We can change the working directory with the cwd option.

For example, we can write:

const exec = require('child_process').exec;

exec('pwd', {
  cwd: '/foo/bar/baz'
}, (error, stdout, stderr) => {
  // work with result
});

We call exec with an object with the cwd property to set the current working directory.

Then we get the result in the callback.

Upload a Binary File to S3 using AWS SDK for Node.js

We can upload a binary file to S3 using the Node.js AWS SDK by using the AWS package.

For instance, we can write:

const AWS = require('aws-sdk');
const fs = require('fs');

AWS.config.update({ accessKeyId: 'key', secretAccessKey: 'secret' });

const fileStream = fs.createReadStream('zipped.tgz');

fileStream.on('error', (err) => {
  if (err) {
    console.log(err);
  }
});

fileStream.on('open', () => {
  const s3 = new AWS.S3();
  s3.putObject({
    Bucket: 'bucket',
    Key: 'zipped.tgz',
    Body: fileStream
  }, (err) => {
    if (err) {
     throw err;
    }
  });
});

We use the aws-sdk package.

First, we authenticate with AWS.config.update .

Then we create a read stream from the file with createReadStream .

Then we listen to the file being opened with by attaching a listener to the 'open' event.

We then create an AWS.S3 instance.

And we call putObject to upload the file.

Bucket is the bucket name.

Key is the path to the file.

Body is the read stream of the file we created.

We also listen to the error event in case any errors are encountered.

Conclusion

We can get the path of the request with the request.url property if we’re using the http module to listen to requests.

To convert relative to absolute paths, we can use the path module’s resolve method.

We can upload files with S3 by creating a read stream and call putObject .

We can set the current working directory with exec .