Classes stop being classes

subclass.js

'use strict';

function typeOf( item ){
    if(item === null) {
        return 'null';
    } else if(item === undefined) {
        return 'undefined';
    }

    if( typeof item.$family == 'function' ){
        return item.$family();
    }

    if( !!item.$class ){
        return 'class';
    }

    return ( Object.prototype.toString.call( item ) ).toLowerCase()
}

class Test extends Uint8ClampedArray{
    constructor(){
        super( 4 );
    }

    $family(){
        return 'test';
    }
}

for( let idx = 0; idx < 1000; idx++ ){
    console.log( typeOf( new Test() ) );
}