Custom function for Google Sheets to Title case an array, range or single value. *Needs work* test function fails to correctly capitalise 'McCartney'

TitleCase.js

/*
 *  Function accepts a single ceel, array, 1D or 2D range Values.
 */
function titleCase(val) {
  return processVal_(val);
}

function processVal_(val) {
  var a;
  if (val.constructor === Array) {
    for (a = 0; a < val.length; a += 1) {
      val[a] = processVal(val[a]);
    }
  } else {
    val = toTitleCase(val);
  }
  return val;
}

function toTitleCase_(str) {
  return str.replace(/([^\W_]+[^\s-]*) */g, function (match, p1, index, title) {
    if (index > 0 && index + p1.length !== title.length &&
      p1.search(smallWords) > -1 && title.charAt(index - 2) !== ":" &&
      title.charAt(index - 1).search(/[^\s-]/) < 0) {
      return match.toLowerCase();
    }
    if (p1.substr(1).search(/[A-Z]|\../) > -1) {
      return match;
    }
    return match.charAt(0).toUpperCase() + match.substr(1);
  });
}

function testTitleCase2() {
  Logger.log(titleCase([['john lennon','paul mcCartney'],['robert scoble'],['tony blair','bobby tables','george bush']]));
}