es6.math.fround.js

// 20.2.2.16 Math.fround(x)
var $export   = require('./_export')
  , sign      = require('./_math-sign')
  , pow       = Math.pow
  , EPSILON   = pow(2, -52)
  , EPSILON32 = pow(2, -23)
  , MAX32     = pow(2, 127) * (2 - EPSILON32)
  , MIN32     = pow(2, -126);

var roundTiesToEven = function(n){
  return n + 1 / EPSILON - 1 / EPSILON;
};


$export($export.S, 'Math', {
  fround: function fround(x){
    var $abs  = Math.abs(x)
      , $sign = sign(x)
      , a, result;
    if($abs < MIN32)return $sign * roundTiesToEven($abs / MIN32 / EPSILON32) * MIN32 * EPSILON32;
    a = (1 + EPSILON32 / EPSILON) * $abs;
    result = a - (a - $abs);
    if(result > MAX32 || result != result)return $sign * Infinity;
    return $sign * result;
  }
});