javascript - 金额,保留两位小数,四舍五入

Question

问题:数字要保留两位小数,但是重写toFixed,大部分数据已经可以四舍五入,但是1.005类似的数据,四舍五入之后得到的数据是1.00,其实应该是1.01,求大神指点;

Number.prototype.toFixed = function (num) {

var changenum = (Number(this * Math.pow(10, num) + 0.5) / Math.pow(10, num)).toString();
index = changenum.indexOf(".");
if (index < 0 && num > 0) {
    changenum = changenum + ".";
    for (i = 0; i < num; i++) {
        changenum = changenum + "0";
    }
} else {
    index = changenum.length - index;
    for (i = 0; i < (num - index) + 1; i++) {
        changenum = changenum + "0";
    }
}
return changenum;

};

Answer 1

1.005*100=100.5，Math.round四舍五入，得101再除100得1.01，能不能这样

Answer 2

写的不大细

<script>
    function change(num) {
                if(typeof num != 'number') {
                    return
                }
                var numStr = num.toString();
                var index = numStr.indexOf('.')
                if(index == -1) {
                    return numStr += '.00'
                } else if(numStr.length - index == 2) {
                    return numStr += '0'
                } else if(numStr.length - index == 3) {
                    return numStr
                } else {
                    var reg = /.(\d{3})\d*$/;
                    newNum = numStr.replace(reg, function($0, $1) {
                        //tempDec 用来判断四舍五入后小数位数
                        var tempDec = Math.round(Number($1.substring(0, 2) + '.' + $1.substring(2)));
                        var newDec;
                        tempDec = tempDec.toString();
                        tempDec == 0 ? newDec = '00' : (tempDec.length == 1 ? newDec = '0' + tempDec : newDec = tempDec)
                        return '.' + newDec
                    })
                }
                return newNum
            }
    </script>

将var reg = /.(d{3})d+$/;改为了var reg = /.(d{3})d*$/;
num != Number改为num != 'number'

Answer 3

function change(money){
    if(typeof money != 'number')return -1;
    return (100*money).toFixed(0)/100;
}
console.log(change(3.005));