Decode 32/64-bit float from bytes in JavaScript

decodeFloat.js

// Derived from http://stackoverflow.com/a/8545403/106786
function decodeFloat(bytes, signBits, exponentBits, fractionBits, eMin, eMax, littleEndian) {
  var totalBits = (signBits + exponentBits + fractionBits);

  var binary = "";
  for (var i = 0, l = bytes.length; i < l; i++) {
    var bits = bytes[i].toString(2);
    while (bits.length < 8) 
      bits = "0" + bits;

    if (littleEndian)
      binary = bits + binary;
    else
      binary += bits;
  }

  var sign = (binary.charAt(0) == '1')?-1:1;
  var exponent = parseInt(binary.substr(signBits, exponentBits), 2) - eMax;
  var significandBase = binary.substr(signBits + exponentBits, fractionBits);
  var significandBin = '1'+significandBase;
  var i = 0;
  var val = 1;
  var significand = 0;

  if (exponent == -eMax) {
      if (significandBase.indexOf('1') == -1)
          return 0;
      else {
          exponent = eMin;
          significandBin = '0'+significandBase;
      }
  }

  while (i < significandBin.length) {
      significand += val * parseInt(significandBin.charAt(i));
      val = val / 2;
      i++;
  }

  return sign * significand * Math.pow(2, exponent);
}

// Sample usage
    ReadSingle: function () {
      var bytes = this.ReadBytes(4);
      return this.$decodeFloat(bytes, 1, 8, 23, -126, 127, true);
    },
    ReadDouble: function () {
      var bytes = this.ReadBytes(8);
      return this.$decodeFloat(bytes, 1, 11, 52, -1022, 1023, true);
    },