fill_in_hatena_diary_twi_content_with_title.user.js

// ==UserScript==
// @name           fillin_hatena_diary_twi_content_with_title
// @namespace      http://shiba-yu36.net/
// @description    fill in hatena diary twitter content with title in edit.
// @include        http://d.hatena.ne.jp/*/edit
// @include        http://d.hatena.ne.jp/*/#edit_in_place
// ==/UserScript==

(function(){

    //その場編集時のアクション
    var editInPlaceAction = function() {

        var fillInTwitterEditInPlace = function(e) {
            if (e.target.name == 'title') {
                var title = e.target;
                var twitter_prefix = title.form.elements.namedItem('twitter_notification_prefix');
                twitter_prefix['focus']();
                twitter_prefix['blur']();
                twitter_prefix.value = title.value;
                twitter_prefix.style.color = "";
            }
        };

        document.addEventListener('change', fillInTwitterEditInPlace, true);
    };

    //詳細編集時のアクション
    var detailEditAction = function() {
        //twitter_contentにfillin
        var fillInTwitterContentInDetail = function(value) {
            var res_snap;
            res_snap = document.evaluate('//*[@id="twitter_notification_prefix"]',
                                         document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
            var twitter_notifier = res_snap.snapshotItem(0);
            twitter_notifier.value = value;
        };

        //編集のtextareaをパースする
        var textareaParseAndFillin = function (){
            var res_snap = document.evaluate('//*[@id="textarea-edit"]',
                                             document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
            var textarea = res_snap.snapshotItem(0);
            var text = textarea.value;
            var text_array = text.split("\n");
            for(var i=0; i<text_array.length; i++) {
                if (text_array[i].match(/^\*\s*[^*]+/)) {
                    var title = text_array[i].replace(/\*\s*/, "");
                    fillInTwitterContentInDetail(title);
                    return;
                }
            }
            fillInTwitterContentInDetail(null);
        };

        //3秒ごとにfillin
        var timer = window.setInterval(textareaParseAndFillin, 3000);
        var res_snap = document.evaluate('//*[@id="twitter_notification_prefix"]',
                                         document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
        //twitter_notifierがフォーカスされたらfillinしなくする
        res_snap.snapshotItem(0).addEventListener('focus',
                                                  function(){
                                                      window.clearInterval(timer);
                                                  },false);
    };

    //URLで挙動を変える
    if (/\#edit_in_place/.test(window.location.href)) {
        editInPlaceAction();
    }
    else {
        detailEditAction();
    }
})();

var が抜けていたので、修正