Examining how nodejs does blocking / async / promises

output.txt

1
2
3
5
Async timeout queued to fire in 3 seconds...
BLOCK for 10 seconds...
sleep 1
sleep 2
sleep 3
sleep 4
sleep 5
sleep 6
sleep 7
sleep 8
sleep 9
sleep 10
8
4
7
6

test.js

function blockingSleep(time) {
  var stop = new Date().getTime();
  while(new Date().getTime() < stop + time) {
    ;
  }
  return;
}

function resolveInSeconds(sec) {
  return new Promise((resolve) => {
    setTimeout(() => { resolve(); }, sec * 1000);
  });
}


console.log(1);
var x = new Promise((resolve) => {
  console.log(2);
  resolve();
});

console.log(3);

x.then(() => { console.log(4); });

console.log(5);

console.log('Async timeout queued to fire in 3 seconds...');
resolveInSeconds(3).then(() => { console.log(6); });

x.then(() => { console.log(7); });

console.log('BLOCK for 10 seconds...');
for (var i =0; i < 10; i++) {
  console.log('sleep '+ (i+1));
  blockingSleep(1000);
}

console.log(8);