   urlIdx ++;
    crawNext();
  });
}
// 下載一個網頁
function pageDownload(url, callback) {
  http.get(url, function(res) {
    res.on('data', callback);
  }).on('error', function(e) {
    console.log("Got error: " + e.message);
  });
}
// 取得正規表達式比對到的結果成為一個陣列
function getMatches(string, regex, index) {
    index || (index = 1); // default to the first capturing group
    var matches = [];
    var match;
    while (match = regex.exec(string)) {
        matches.pus