Run results for: Type discriminators

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36

Browser: Chrome 104

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
instanceof	4521298.0 Ops/sec
string discriminant	4017750.0 Ops/sec
number discriminant	4267082.0 Ops/sec
property exists w/ in operator	9795969.0 Ops/sec
constructor comparison	2927501.0 Ops/sec

HTML Preparation code:

<script>
    class A {
        constructor() {
            this.i = 1
            this.n = 'A'
            this.aOnly = 0
        }
    }
  
  	A.NAME = 'A'
  	A.NUM = 1

    class B {
        constructor() {
            this.i = 2
            this.n = 'B'
            this.bOnly = 0
        }
    }
  
  	B.NAME = 'B'
  	B.NUM = 2
</script>

Script Preparation code:

var obj = new A();

Tests:

instanceof
obj instanceof A;
string discriminant
obj.n === A.NAME
number discriminant
obj.i === A.NUM
property exists w/ in operator
'aOnly' in obj
constructor comparison
obj.constructor === A

Run results for: Type discriminators

Measure the performance of instanceOf operator vs comparing other types.

instanceof

string discriminant

number discriminant

property exists w/ in operator

constructor comparison