Run results for: Fastest way to find keys in objects

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:138.0) Gecko/20100101 Firefox/138.0

Browser: Firefox 138

Operating system: Ubuntu

Device Platform: Desktop

Date tested: one year ago

Benchmark engine: Benchmark.js

14.1M/s

undefined

13.6M/s

hasOwnProperty

10.8M/s

View exact numbers

Test name	Executions per second
✓ in	14,061,618 Ops/sec
undefined	13,626,743 Ops/sec
hasOwnProperty	10,824,985 Ops/sec

Script Preparation code:

source = {
    a: 1,
    b: 2,
    c: 3,
    d: 4,
    e: 5,
    f: 6,
    g: 7,
    h: 8,
};
target = {
    a: 1,
    b: 2,
    d: 4,
    e: 5,
    f: 6,
    i: 9,
    j: 10,
};

Tests:

undefined
for (const sourceKey in source) { if (target[sourceKey] === undefined) { delete target.sourceKey; } }
hasOwnProperty
for (const sourceKey in source) { if (!target.hasOwnProperty(sourceKey)) { delete target.sourceKey; } }
in
for (const sourceKey in source) { if (!(sourceKey in target)) { delete target.sourceKey; } }