Piと序数を対応表示させてみる
<script>
var arr = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9];
arr.forEach(function (x, y) {
console.log( '['+y+ '→'+ x+ ']');
});
</script>
<script>
var arr = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9];
arr.forEach(function (x, y) {
console.log( '['+y+ '→'+ x+ ']');
});
</script>