delay_in_javascript.md

Task

console.log '1' after 1 second,
'2' after 2 seconds and
'3' after 3 seconds after start of the program.

setTimeout

The delay parameter only guarantees that your callback will not execute before that time has elapsed. Other queued tasks or operations could delay it further than the specified time.

const startTime = process.hrtime();

console.log('startTime: ', startTime);
for (let i = 1; i < 4; i++) {
    setTimeout(() => {
        console.log('Message ' + i + ' ', process.hrtime());
    }, i * 1000);
}

Output

startTime: [ 20341, 488209050 ]
Message 1 [ 20342, 499922394 ]
Message 2 [ 20343, 498388755 ]
Message 3 [ 20344, 498487014 ]

console.log('startTime: ', startTime);
for (let i = 1; i < 4; i++) {
    setTimeout(() => {
        console.log('Message ' + i + ' ', process.hrtime(startTime));
    }, i * 1000);
}

Output

startTime: [ 20482, 505385747 ]
Message 1 [ 1, 13938178 ]
Message 2 [ 2, 13741552 ]
Message 3 [ 3, 13861540 ]

for (let i = 1; i < 4; i++) {
    setTimeout(() => {
        console.log('Message ' + i + ' ', process.uptime());
    }, i * 1000);
}

Output

Message 1 1.10126115
Message 2 2.102194643
Message 3 3.102512365

setInterval

const startTime = process.hrtime();
console.log('startTime: ', startTime);

let i = 1;
const interval = setInterval(() => {
    console.log('Message ' + i + ' ', process.hrtime());
    i++;
    if (i > 3) {
        clearInterval(interval);
    }
}, 1000);

Output

startTime: [ 21511, 206821155 ]
Message 1 [ 21512, 217929990 ]
Message 2 [ 21513, 218730640 ]
Message 3 [ 21514, 218790140 ]

const startTime = process.hrtime();
console.log('startTime: ', startTime);

let i = 1;
const interval = setInterval(() => {
    console.log('Message ' + i + ' ', process.hrtime(startTime));
    i++;
    if (i > 3) {
        clearInterval(interval);
    }
}, 1000);

Output

startTime: [ 21356, 295521886 ] Message 1 [ 1, 10849822 ] Message 2 [ 2, 11730624 ] Message 3 [ 3, 14871246 ]

let i = 1;
const interval = setInterval(() => {
    console.log('Message ' + i + ' ', process.uptime());
    i++;
    if (i > 3) {
        clearInterval(interval);
    }
}, 1000);

Output

Message 1 1.094841971
Message 2 2.09636721
Message 3 3.098306832

const intervalId = setInterval(() => {
console.log('Runs every 2 seconds');
}, 2000);

// Stop after 10 seconds
setTimeout(() => clearInterval(intervalId), 10000);