サンプルかいてみたぞい <script type="text/javascript" src="prototype-1.6.0.3.js"></script> <script language="JavaScript"> var arrayid = new Array(); var arraynum = new Array(); function nullpo(drop){ if (arrayid.indexOf(drop.id) == -1) { arrayid.push(drop.id); arraynum.push(drop.value); } else { arraynum[arrayid.indexOf(drop.id)] = drop.value; } var sum = 0; for (i=0; i< arraynum.length; i++) { sum = sum + parseInt(arraynum[i]); } alert(sum); } </script>