Node.js is single-threaded, just like the web. To handle long running operations it also uses a callback pattern. The callback pattern in Node.js has a a few more details to it and can be described as having the following properties:
- There is only one function to handle success and error responses
- The callback is called only once
- The function is the last parameter of the calling function
- The callback consists of the parameter's errors and results, in that order, which is also called error-first
Let's now showcase what the calling code looks like, with a callback supplied as the function's last argument:
callAsync('1',2, (error, response) => { if(error) { console.error(error); } else { console.log('response', ...
