Run results for: Map.get() !== undefined VS Map.has() + .get()

Performance comparison of Map.get() !== undefined to check if element exists and Map.has() as most of the time you need the element after the .has() check anyway. LIMITATION: The checks are not completely the same. If the map contains a key whose value is intentionally set to undefined (Map.set(1, undefined)), .has() will return true, while the .get() !== undefined will be false.

Go to the benchmark

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0

Browser: Firefox 140

Operating system: Linux

Device Platform: Desktop

Date tested: 9 months ago

Test name	Executions per second
Map.get() !== undefined	82031.6 Ops/sec
Map.has() + .get()	71243.7 Ops/sec

Script Preparation code:

var i = 0,
    count = 1000,
    a;
var map = new Map();

for (i = 0; i < count; i++) {
    if (Math.random() > 0.5) {
        map.set(i, i * i);
    }
}

Tests:

Map.get() !== undefined
for (i = 0; i < count; i++) { const v = map.get(i); if (v !== undefined) { a = v; } }
Map.has() + .get()
for (i = 0; i < count; i++) { if (map.has(i)) { a = map.get(i); } }