Run results for: Instanceof vs string comparison vs property checking vs constructor comparison - MeasureThat.net

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser: Chrome 136

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

constructor comparison

286.1M/s

then check

281.0M/s

instanceof Promise

276.0M/s

View exact numbers

Test name	Executions per second
✓ constructor comparison	286,094,048 Ops/sec
then check	281,001,952 Ops/sec
instanceof Promise	276,040,096 Ops/sec

Script Preparation code:

const obj = new Promise(() => {});
const obj2 = {};
const obj3 = null;
const obj4 = undefined;

Tests:

instanceof Promise (promise)
obj instanceof Promise
instanceof Promise (empty object)
obj2 instanceof Promise
instanceof Promise (null)
obj3 instanceof Promise
then check (promise)
obj?.then
then check (empty object)
obj2?.then
then check (null)
obj3?.then
constructor comparison (promise)
obj?.constructor === Promise
constructor comparison (empty object)
obj2?.constructor === Promise
constructor comparison (null)
obj3?.constructor === Promise
type obj?.then === function (promise)
typeof obj?.then === 'function'
type obj?.then === function (empty object)
typeof obj2?.then === 'function'
type obj?.then === function (null)
typeof obj3?.then === 'function'
then in (promise)
obj && 'then' in obj
then in (empty object)
obj2 && 'then' in obj2
then in (null)
obj3 && 'then' in obj3
instanceof Promise (undefined)
obj instanceof Promise
then check (undefined)
obj4?.then
constructor comparison (undefined)
obj4?.constructor === Promise
type obj?.then === function (undefined)
typeof obj4?.then === 'function'
then in (undefined)
obj4 && 'then' in obj4