Why is there a double quote at the beginning of the my result?

I have tried looking for this problem here but still can’t find an answer (maybe I’m too newbie to even write the exact keywords).
I am trying to overcome freecodecamp challenge on “binary agent”, my question is not “How to convert binary to text string” But

why is there a double quote at the beginning of the my result ?

Thank You

    function binaryAgent(str) {
  let binaryArr;
  let decimalArr = [];
  let textArr = [];
  let joinTextArr;
  for (let i=0; i<str.length; i++){
    // convert binary to decimal use parseInt(value, radix)
    binaryArr = str.split(" ");
    decimalArr.push(parseInt(binaryArr[i], 2));
    decimalArr = decimalArr.filter( value => !Number.isNaN(value) );
    // convert decimal to text
    textArr.push(String.fromCharCode(decimalArr[i]))
    // join to be a string
    joinTextArr = textArr.join("")
  }
  return joinTextArr;
}

console.log(binaryAgent("01000001 01110010 01100101 01101110 00100111 01110100 00100000 01100010 01101111 01101110 01100110 01101001 01110010 01100101 01110011 00100000 01100110 01110101 01101110 00100001 00111111"));

// result > "Aren't bonfires fun!?