金额显示，每3位加逗号

function format_number(n) {
    n = n + '';
    var re = /^-?[0-9]+.?[0-9]*$/;
    if (!re.test(n)) {
        return n;
    }
    var pos = n.indexOf(".");
    var part1;
    var part2;
    if (pos > -1) {
        part1 = n.substr(0, pos);
        part2 = n.substr(pos + 1);
    } else {
        part1 = n;
    }
    var sign = '';
    if (part1.indexOf('-') > -1) {
        sign = part1.slice(0, 1);
        part1 = part1.slice(1);
    }
    var len = part1.length;
    if (len > 3) {
        var r = len % 3;
        part1 = r > 0 ? part1.slice(0, r) + "," + part1.slice(r, len).match(/\d{3}/g).join(",") : part1.slice(r, len).match(/\d{3}/g).join(",");
    }
    if (part2) {
        return sign + part1 + '.' + part2;
    } else {
        return sign + part1;
    }
};

效果如下；

1234.01 ⇒1,234.01

-1234.01 ⇒-1,234.01