How asynchronous JavaScript works under the hood

Hi, Today, I watched an amazing tutorial video about JavaScript asynchronous feature and learned how it works under the hood.

Exercise 1

Write the order of 3 function executions

function printHello () {
    console.log('Hello');
}

function blockFor1Sec () {
    //assume looping on huge array and it takes approximately 1 second to complete
}

setTimeout(printHello, 0);

blockFor1Sec();

console.log('Me first!');

What happens under the hood

Answer for exercise 1

• blockFor1Sec (1ms - 1001ms)
• 'Me first!' (1002ms)
• 'Hello' (1003ms)