es6.number.to-fixed.js

'use strict';
var $export      = require('./_export')
  , anInstance   = require('./_an-instance')
  , toInteger    = require('./_to-integer')
  , aNumberValue = require('./_a-number-value')
  , repeat       = require('./_string-repeat')
  , $toFixed     = 1..toFixed
  , floor        = Math.floor
  , data         = [0, 0, 0, 0, 0, 0]
  , ERROR        = 'Number.toFixed: incorrect invocation!'
  , ZERO         = '0';

var multiply = function(n, c){
  var i  = -1
    , c2 = c;
  while(++i < 6){
    c2 += n * data[i];
    data[i] = c2 % 1e7;
    c2 = floor(c2 / 1e7);
  }
};
var divide = function(n){
  var i = 6
    , c = 0;
  while(--i >= 0){
    c += data[i];
    data[i] = floor(c / n);
    c = (c % n) * 1e7;
  }
};
var numToString = function(){
  var i = 6
    , s = '';
  while(--i >= 0){
    if(s !== '' || i === 0 || data[i] !== 0){
      var t = String(data[i]);
      s = s === '' ? t : s + repeat.call(ZERO, 7 - t.length) + t;
    }
  } return s;
};
var pow = function(x, n, acc){
  return n === 0 ? acc : n % 2 === 1 ? pow(x, n - 1, acc * x) : pow(x * x, n / 2, acc);
};
var log = function(x){
  var n  = 0
    , x2 = x;
  while(x2 >= 4096){
    n += 12;
    x2 /= 4096;
  }
  while(x2 >= 2){
    n  += 1;
    x2 /= 2;
  } return n;
};

$export($export.P + $export.F * (!!$toFixed && (
  0.00008.toFixed(3) !== '0.000' ||
  0.9.toFixed(0) !== '1' ||
  1.255.toFixed(2) !== '1.25' ||
  1000000000000000128..toFixed(0) !== '1000000000000000128'
) || !require('./_fails')(function(){
  // V8 ~ Android 4.3-
  $toFixed.call({});
})), 'Number', {
  toFixed: function toFixed(fractionDigits){
    var x = aNumberValue(this, ERROR)
      , f = toInteger(fractionDigits)
      , s = ''
      , m = ZERO
      , e, z, j, k;
    if(f < 0 || f > 20)throw RangeError(ERROR);
    if(x != x)return 'NaN';
    if(x <= -1e21 || x >= 1e21)return String(x);
    if(x < 0){
      s = '-';
      x = -x;
    }
    if(x > 1e-21){
      e = log(x * pow(2, 69, 1)) - 69;
      z = e < 0 ? x * pow(2, -e, 1) : x / pow(2, e, 1);
      z *= 0x10000000000000;
      e = 52 - e;
      if(e > 0){
        multiply(0, z);
        j = f;
        while(j >= 7){
          multiply(1e7, 0);
          j -= 7;
        }
        multiply(pow(10, j, 1), 0);
        j = e - 1;
        while(j >= 23){
          divide(1 << 23);
          j -= 23;
        }
        divide(1 << j);
        multiply(1, 1);
        divide(2);
        m = numToString();
      } else {
        multiply(0, z);
        multiply(1 << -e, 0);
        m = numToString() + repeat.call(ZERO, f);
      }
    }
    if(f > 0){
      k = m.length;
      m = s + (k <= f ? '0.' + repeat.call(ZERO, f - k) + m : m.slice(0, k - f) + '.' + m.slice(k - f));
    } else {
      m = s + m;
    } return m;
  }
});