Learning Node.js Development

The working of blocking I/O

The blocking example can be illustrated as follows:

The first thing that happens inside our blocking example, as shown in the preceding screenshot, is that we fetch the user on line 3 in the code:

var user1 = getUserSync('123');

Now, this request requires us to go to a database, which is an I/O operation to fetch that user by ID. This takes a little bit of time. In our case, we'll say it takes three seconds.

Next, on line 4 in the code, we print the user to the screen, which is not an I/O operation and it runs right away, printing user1 to the screen, as shown in the following code:

console.log('user1', user1); ...