Number.prototype.toFixed =
function(fractionDigits) {
var f = parseInt(fractionDigits) ||
0;
if( f < -
20 || f >
100 ) {
throw new RangeError(
"Precision of " + f +
" fractional digits is out of range");
}
var x = Number(
this);
if( isNaN(x) ) {
return "NaN";
}
var s =
"";
if(x <=
0) {
s =
"-";
x = -
x;
}
if( x >= Math.pow(
10,
21) ) {
return s +
x.toString();
}
var m;
// 10. Let n be an integer for which the exact mathematical value of
// n ÷ 10^f - x is as close to zero as possible.
// If there are two such n, pick the larger n.
n = Math.round(x * Math.pow(
10, f) );
if( n ==
0 ) {
m =
"0";
}
else {
// let m be the string consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
m =
n.toString();
}
if( f ==
0 ) {
return s +
m;
}
var k =
m.length;
if(k <=
f) {
var z = Math.pow(
10, f+
1-k).toString().substring(
1);
m = z +
m;
k = f+
1;
}
if(f >
0) {
var a = m.substring(
0, k-
f);
var b = m.substring(k-
f);
m = a +
"." +
b;
}
return s +
m;
};
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