javascript tofixed四舍五入的方法详解编程语言

javascript tofixed四舍五入的方法

Number.prototype.toFixed = function(d) {
 var s = this + "";
 if (!d) d = 0;
 if (s.indexOf(".") == -1) s += ".";
 s += new Array(d + 1).join("0");
 if (new RegExp("^(-|//+)?(//d+(//.//d{0," + (d + 1) + "})?)//d*$").test(s)) {
 var s = "0" + RegExp.$2,
 pm = RegExp.$1,
 a = RegExp.$3.length,
 b = true;
 if (a == d + 2) {
 a = s.match(//d/g);
 if (parseInt(a[a.length - 1]) > 4) {
 for (var i = a.length - 2; i >= 0; i--) {
 a[i] = parseInt(a[i]) + 1;
 if (a[i] == 10) {
 a[i] = 0;
 b = i != 1;
 } else break;
 }
 }
 s = a.join("").replace(new RegExp("(//d+)(//d{" + d + "})//d$"), "$1.$2");
 }
 if (b) s = s.substr(1);
 return (pm + s).replace(//.$/, "");
 }
 return this + "";
};