js数值四舍五入格式化

深藏阁楼爱情的钟 2022-07-12 01:21 141阅读 0赞

/* 将数值四舍五入后格式化. @param num 数值(Number或者String) @param cent 要保留的小数位(Number) @param isThousand 是否需要千分位 0:不需要,1:需要(数值类型); @return 格式的字符串,如'1,234,567.45' @type String */ 
        function formatNumber(num,cent,isThousand){ 
            num = num.toString().replace(/\$|\,/g,''); 
            if(isNaN(num))//检查传入数值为数值类型. 
            num = "0"; 
            if(isNaN(cent))//确保传入小数位为数值型数值. 
            cent = 0; 
            cent = parseInt(cent); 
            cent = Math.abs(cent);//求出小数位数,确保为正整数. 
            if(isNaN(isThousand))//确保传入是否需要千分位为数值类型. 
            isThousand = 0; 
            isThousand = parseInt(isThousand); 
            if(isThousand < 0) 
            isThousand = 0; 
            if(isThousand >=1) //确保传入的数值只为0或1 
            isThousand = 1; 
            sign = (num == (num = Math.abs(num)));//获取符号(正/负数) 
            //Math.floor:返回小于等于其数值参数的最大整数 
            num = Math.floor(num*Math.pow(10,cent)+0.50000000001);//把指定的小数位先转换成整数.多余的小数位四舍五入. 
            cents = num%Math.pow(10,cent); //求出小数位数值. 
            num = Math.floor(num/Math.pow(10,cent)).toString();//求出整数位数值. 
            cents = cents.toString();//把小数位转换成字符串,以便求小数位长度. 
            while(cents.length<cent){
       //补足小数位到指定的位数. 
                cents = "0" + cents;
            } 
            if(isThousand == 0) //不需要千分位符. 
            return (((sign)?'':'-') + num + '.' + cents); 
            //对整数部分进行千分位格式化. 
            for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++) 
            num = num.substring(0,num.length-(4*i+3))+','+ 
            num.substring(num.length-(4*i+3));
            if(cents != 0){
                return (((sign)?'':'-') + num + '.' + cents); 
            } else {
                return (((sign)?'':'-') + num + '.00');
            }
        }