数字之间加逗号

/** * 数字之间加逗号 * @param{String}参数 * @return{String}返回结果 */function formatNum(str){str = str.toString();if (/[^0-9\.]/.test(str)){return str;}var strFloor = '';if(RegExp('\\.').test(str)){strArr = str.split('.');str = strArr[0];strFloor = '.' + strArr[1];}    var n = str.length % 3;    if(n){        return str.slice(0,n) +  str.slice(n).replace(/(\d{3})/g,',$1') + strFloor;    }else{        return str.replace(/(\d{3})/g,',$1').slice(1) + strFloor;    }};var str1 = formatNum("12345678990");var str2 = formatNum("12345678990.25");var str3 = formatNum("32%");var str4 = formatNum("$525");console.log(str1);// 12,345,678,990console.log(str2);// 12,345,678,990.25console.log(str3);// 32%console.log(str4);// $525