js原始碼：

<script>
    function show(s) {
        var re= '';
        var length = s.length;
        for (var i = 0,j=1; i < length; i++,j++) {
            if (j&&j % 6 == 0) {
                re += '<br />';
            } else {
                re += s[i];
            }
        }
        return 
 
re;
    }
    var a = '123456789012345667890';
    document.write(show(a));
</script>

思路：當一行有5個字元的時候，新增一個<br>換行標籤