code: function joinURL (urlA, urlB) {
    urlA = urlA || "";
    urlB = urlB || "";
  
    let endsWithASlash = urlA.substr(-1) === "/" || urlA.substr(-1) === "\\";
    let startsWithASlash = urlB[0] === "/" || urlB[0] === "\\";
  
    if (endsWithASlash || startsWithASlash) {
      return urlA + urlB;
    }
    else {
      return urlA + "/" + urlB;
    }
  }
docs: Joins two URL paths, possibly adding a separator.
  
  @param {string} urlA
  @param {string} urlB
  @returns {string}