在javascript中截断(不舍入)十进制数字 [英] Truncate (not round off) decimal numbers in javascript
问题描述
5.467 - > 5.46
985.943 - > 985.94
toFixed(2)
正确的事情,但它取决于价值。我不需要四舍五入的价值。希望这可以在JavaScript中。
upd :
因此,事实证明,无论你多么努力地补偿他们,四舍五入的错误总会困扰着你。因此,应该通过用十进制表示法来表示数字来攻击问题。
Number.prototype.toFixedDown = function(digits){
var re = new RegExp((\\ d + \\\\\\\\\\\\\\\\\)的ToString()匹配(重新)。
返回m? parseFloat(m [1]):this.valueOf();
};
[5.467.toFixedDown(2),
985.943.toFixedDown(2),
17.56.toFixedDown(2),
(0).toFixedDown(1) ,
1.11.toFixedDown(1)+ 22];
$ b $ // [5.46,985.94,17.56,0,23.1]
基于他人编译的老错误解决方案:
pre $ Number $原型.toFixedDown =函数(数字){
var n = this - Math.pow(10,-digits)/ 2;
n + = n / Math.pow(2,53); //添加1360765523:17.56.toFixedDown(2)===17.56
return n.toFixed(digits);
}
I am trying to truncate decimal numbers to decimal places. Something like this:
5.467 -> 5.46
985.943 -> 985.94
toFixed(2)
does just about the right thing but it rounds off the value. I don't need the value rounded off. Hope this is possible in javascript.
upd:
So, after all it turned out, rounding bugs will always haunt you, no matter how hard you try to compensate them. Hence the problem should be attacked by representing numbers exactly in decimal notation.
Number.prototype.toFixedDown = function(digits) {
var re = new RegExp("(\\d+\\.\\d{" + digits + "})(\\d)"),
m = this.toString().match(re);
return m ? parseFloat(m[1]) : this.valueOf();
};
[ 5.467.toFixedDown(2),
985.943.toFixedDown(2),
17.56.toFixedDown(2),
(0).toFixedDown(1),
1.11.toFixedDown(1) + 22];
// [5.46, 985.94, 17.56, 0, 23.1]
Old error-prone solution based on compilation of others':
Number.prototype.toFixedDown = function(digits) {
var n = this - Math.pow(10, -digits)/2;
n += n / Math.pow(2, 53); // added 1360765523: 17.56.toFixedDown(2) === "17.56"
return n.toFixed(digits);
}
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