We only need one dependency, the core http module. Let's require it:

const http = require('http') 

Now let's define a payload we wish to POST to an endpoint:

const payload = `{ 
  "name": "Cian O Maidín", 
  "company": "nearForm" 
}` 

Now we'll define the configuration object for the request we're about to make:

const opts = { 
  method: 'POST', 
  hostname: 'reqres.in', 
  port: 80, 
  path: '/api/users', 
  headers: { 
    'Content-Type': 'application/json', 
    'Content-Length': Buffer.byteLength(payload) 
  } 
} 

Notice how we use Buffer.byteLength to determine the Content-Length header.

Next we'll make the request, supplying a callback handler which will be called once the request has completed:

const req = http.request(opts, (res) => { 
  console.log('
  Status: ' + res.statusCode) 
  process.stdout.write('  Body: ') 
  res.pipe(process.stdout) 
  res.on('end', () => console.log('
')) 
}) 

Let's not forget to handle errors:

req.on('error', (err) => console.error('Error: ', err)) 

Finally, the most important part, sending the payload:

req.end(payload) 

Now if we execute our script:

$ node index.js

Providing the website reqres.in is functioning correctly, we should see something like the following: