Amateur (Ham) Radio US Vanity Callsign Rules for Javascript

callsigns.js

// http://www.arrl.org/vanity-call-signs
String.prototype.isValidCallsign = function() {
  const sign = this.toString().toUpperCase().trim();
  // quick obvious check that might save time in large sets
  if (sign.length < 3 || sign.length > 6) {
    return false;
  }
  // the general structure of the us callsign
  var validSign = /^[AKNW][A-Z]?[0-9][A-Z]{1,3}$/;
  if (!validSign.test(sign)) {
    return false;
  }
  // it's a valid sign so far. now to test if it breaks
  // specific fcc rules about what it can't be
  var rule1 = /^KA[2-9][A-Z]{2}$/.test(sign);
  var rule2 = /^KC4AA[A-F]$/.test(sign);
  var rule3 = /^KC4US[A-Z]$/.test(sign);
  var rule4 = /^KG4[A-Z]{2}$/.test(sign);
  var rule5 = /^KC6[A-Z]{2}$/.test(sign);
  var rule6 = /^KL9K[A-H][A-Z]$/.test(sign);
  var rule7 = /^KX6[A-Z]{2}$/.test(sign);
  var rule8 = /SOS/g.test(sign);
  var rule9 = /Q[R-U][A-Z]/g.test(sign);
  var rule10 = /^A[M-Z]/.test(sign);
  var rule11 = sign.length == 6 && sign.charAt(3) == "X";
  var rule12 = /^[AKNW]F[0-9]EMA$/.test(sign);
  var rule13 = sign.length == 6 && /^A{A-L}/.test(sign);
  var rule14 = sign.length == 6 && /^N[A-Z]/.test(sign);
  var rule15 = sign.length == 6 && /^W[CKMRT]/.test(sign);
  var rule16 = /^[KNW]P[06789]/.test(sign);
  var rule17 = /^[KNW][0-9][A-Z]$/.test(sign);
  // does it break any of the rules?
  var breaksRules = rule1 || rule2 || rule3 || rule4 || rule5 || rule6 || rule7 || rule8 || rule9 || rule10 || rule11 || rule12 || rule13 || rule14 || rule15 || rule16 || rule17;
  return !breaksRules;
}

usage.js

console.log("kd8vyx".isValidCallsign());
console.log("blah".isValidCallsign());
console.log("aa8aa".isValidCallsign());