有可能在JavaScript中编写PHP逻辑吗？

Is it possible to write PHP logic in Javascript? I have this script but does not work well. Variable that appears always to the first criteria.

 <script>
    function subtotal(konversi){
        console.log('subtotal function');
        for(var j = 1; j < <?php echo"$cek";?>+1; j++){

            //First Criteria
            <?php if ($uom['uom_name'] =='KG') { ?> 
                var hitung = (document.getElementById('quantity'+j).value * document.getElementById('packing_value'+j).value);
            <?php } ?>

            //Second Criteria
            <?php if ($uom['uom_name'] =='MC') { ?> 
                var hitung = (document.getElementById('quantity'+j).value / document.getElementById('packing_value'+j).value);
             <?php } ?>

            document.getElementById('quantity_konversi'+j).value = hitung; 
            console.log(j, hitung);
        }
    } 
</script>

Please help me out and explain in detail because I am a newbie! Thanks

PHP executes on the server and is completed before it hits the browser. That's where JS comes in to play. There are techniques for the two to communicate (AJAX for example) but otherwise they serve different purposes.