Redmine Ticket Form Enter-submit Canceller

gistfile1.js

// ==UserScript==
// @name       Redmine Ticket Form Enter-submit Canceller
// @namespace  http://iss.ms/
// @version    0.1
// @description  チケット登録フォームの「題名」入力時，Enterを押してもsubmitされなくなります．
// @include    https://*/*
// @copyright  issm
// ==/UserScript==
var _form    = document.getElementById('issue-form')
  , _subject = document.getElementById('issue_subject')
;
if ( _form  &&  _subject ) {
    var _handle_form_submit = function (ev) {
        return false;
    };
    _subject.addEventListener('focus', function (ev) {
        //_form.addEventListener('submit', _handle_form_submit);  // うまくいかん
        _form.onsubmit = _handle_form_submit;
    });
    _subject.addEventListener('blur', function (ev) {
        //_form.removeEventListener('submit', _handle_form_submit);
        _form.onsubmit = null;
    });
    _subject.blur();
    _subject.focus();
}