Takes a Binary string and will return its signed decimal value

TwosComplement.js

function binaryTwosComplementToInt(binaryString) {
  if (binaryString[0] != 1) { 
    return parseInt(binaryString, 2); 
  }

  let twosComplementResult = "";

  binaryString.match(/.{1,1}/g).forEach(str => {
    twosComplementResult += (str == 1) ? str = 0 : str = 1;
  });

  return -parseInt(twosComplementResult, 2);
}