From hex to float - Javascript [duplicate]

Question

I am trying to convert a hex string to a float number in Javascript.

Suppose that I have the hex string "0082d241". Using this online converter and selecting Swap endianness, the correct float value is 26,3135.

I know that this is the correct answer because it is from a TMP36 sensor.

I have tried some other examples that I found here on SO, such as Converting hexadecimal to float in javascript, but none of them worked.

Answer 1

The first step is to swap endianness, using the source code found on the page that you've shown.

Then you can convert the hexadecimal string to a float value.

function flipHexString(hexValue, hexDigits) {
  var h = hexValue.substr(0, 2);
  for (var i = 0; i < hexDigits; ++i) {
    h += hexValue.substr(2 + (hexDigits - 1 - i) * 2, 2);
  }
  return h;
}


function hexToFloat(hex) {
  var s = hex >> 31 ? -1 : 1;
  var e = (hex >> 23) & 0xFF;
  return s * (hex & 0x7fffff | 0x800000) * 1.0 / Math.pow(2, 23) * Math.pow(2, (e - 127))
}

console.log(hexToFloat(flipHexString("0x0082d241", 8)));
console.log(hexToFloat(flipHexString("0x5d7e2842", 8)));