Run results for: InstanceOf vs key in obj vs !== null vs string in key

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:124.0) Gecko/20100101 Firefox/124.0

Browser: Firefox 124

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

HTML Preparation code:

<script>
class TestClass {
    constructor() {
        this.a = 2;
        this.t = 'mesh';
    }
}
</script>

Script Preparation code:

var obj = new TestClass();

Tests: