Run results for: instanceof vs regular comparison

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.114 Safari/537.36

Browser: Chrome 89

Operating system: Mac OS X 10.15.4

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Check with regular comparison	1625.3 Ops/sec
Check using instanceof	610.0 Ops/sec

Script Preparation code:

var dateList = [];
var currentDateTime = Date.now();
for (i = 0; i < 10000; i++) {
    var randomInt = Math.round(Math.random()); // This will randomly returns either 0 or 1.
    if (randomInt === 0) {
        dateList.push(null); // Fill the array with a null value.
    } else {
        dateList.push(addMinutes(currentDateTime, i)); // This will fill up the array with date objects.
    }
}

function addMinutes(dt, minutes) {
    return new Date(dt + minutes * 60000);
}

Tests:

Check with regular comparison
var counter = 0; for (i = 0; i < 10000; i++) { if (!!dateList[i]) { counter++; } }
Check using instanceof comparison
var counter = 0; for (i = 0; i < 10000; i++) { if (dateList[i] instanceof Date) { counter++; } }
Check using regular and instanceof comparison
var counter = 0; for (i = 0; i < 10000; i++) { if (!!dateList[i] && dateList[i] instanceof Date) { counter++; } }

Run results for: instanceof vs regular comparison

We try to check if comparing value using regular existence comparison is more efficient than comparing using instanceof.

Check with regular comparison

Check using instanceof comparison

Check using regular and instanceof comparison