JS将数字转换成三位逗号分隔的样式详解编程语言

function formatNumber(num) { 
    if (!/^(/+|-)?(/d+)(/./d+)?$/.test(num)) { 
        return num; 
    } 
    var a = RegExp.$1, b = RegExp.$2, c = RegExp.$3; 
    var re = new RegExp().compile("(//d)(//d{3})(,|$)"); 
    while (re.test(b))   b = b.replace(re, "$1,$2$3"); 
    return a + "" + b + "" + c; 
}