javascript :數字格式化輸出

<script type="text/javascript">

var format = function (number, form) {

    var forms = form.split('.'), number = '' + number, numbers = number.split('.')

        , leftnumber = numbers[0].split('')

        , exec = function (lastMatch) {

            if (lastMatch == '0' || lastMatch == '#') {

                if (leftnumber.length) {

                    return leftnumber.pop();

                } else if (lastMatch == '0') {

                    return lastMatch;

                } else {

                    return '';

                }

            } else {

                return lastMatch;

            }

    }, string

    string = forms[0].split('').reverse().join('').replace(/./g, exec).split('').reverse().join('');

    string = leftnumber.join('') + string;

    if (forms[1] && forms[1].length) {

        leftnumber = (numbers[1] && numbers[1].length) ? numbers[1].split('').reverse() : [];

        string += '.' + forms[1].replace(/./g, exec);

    }

    return string.replace(//.$/, '');

};

alert(format(123, '#.00'))                         //輸出   123.00

alert(format(123, '0.##'))                         //輸出   123

alert(format(123, '0000.00 '))                     //輸出   0123.00

alert(format(123456, '###,###.00'))                //輸出   123,456.00

</script>