javascriptstringhexdecimal

I need to create function which take value from string and edit numbers


I have this string 03.00.20.80.0F.00.00.68.98.01. last two bytes 98.01. have information about temperature. I need to create JavaScript function which convert two last bytes from hexadecimal number 0198 to 19 and 8. This numbers I want to convert from hexadecimal numbers to decimal and sum together. So it gives me number 25.8. It must be variable for whatever number because I can receive other string from my sensor like 03.00.20.80.0F.00.00.54.09.02.

I tried this function but it is return value 0.1

function splitAndConvertHex(hexString) {
  
  const bytes = hexString.split('.');
  
  const lastTwoBytes = bytes.slice(-2).join('');
  
  const hexValue = '0x' + lastTwoBytes;
  
  const intValue = parseInt(hexValue) >> 8;
  const floatValue = (parseInt(hexValue) & 0xFF) / 10;

  return [intValue, floatValue];
}

const hexString = "03.00.20.80.0F.00.00.68.98.01.";
const [wholeNumber, decimalNumber] = splitAndConvertHex(hexString);

const result = wholeNumber + decimalNumber;
console.log("Výsledek: " + result);


Solution

  • Not sure about the logic behind getting 25.8 from 98.01, but this produces the correct value:

    function splitAndConvertHex(hexString) {
      // "03.00.20.80.0F.00.00.68.98.01" --> 198
      let x = parseInt(hexString.split('.').slice(-2).reverse().join(''));
      return [parseInt((x / 10).toString(), 16), parseInt((x % 10).toString(), 16)];
    }
    
    console.log(splitAndConvertHex("03.00.20.80.0F.00.00.68.98.01"));