QuickSearchForm.user.js

// ==UserScript==
// @name           QuickSearchForm
// @namespace      http://june29.jp/
// @include        http://*
// @include        https://*
// ==/UserScript==

(function() {
  var BIND_KEY = '/';

  var searchform = null;

  var firefox;
  if(typeof unsafeWindow != 'undefined'){
    firefox = true;
  } else {
    firefox = false;
  }

  function focusForm() {
    if(searchform) {
      getFirstElementByXPath(searchform).focus();
    }
  }

  var skipEl = {'input': false, 'button': true, 'select': true, 'textarea': false, 'password': false};
  window.addEventListener('keypress', function(e) {
    if (skipEl[e.target.tagName.toLowerCase()]) {return;}
    var key = ''
      + ((e.ctrlKey)  ? 'C' : '')
      + ((e.shiftKey) ? 'S' : '')
        + ((e.altKey || e.metaKey)   ? 'A' : '')
        + '-';
    if(firefox){
      key += String.fromCharCode(e.charCode).toLowerCase();
    }else{
      key += String.fromCharCode(e.keyCode).toLowerCase();
    }
    if (key == "C-"+BIND_KEY){
      focusForm();
    }
  }, false);

  function getFirstElementByXPath(xpath, node) {
    var node = node || document;
    var doc = node.ownerDocument ? node.ownerDocument : node;
    var result = doc.evaluate(xpath, node, null,
                              XPathResult.FIRST_ORDERED_NODE_TYPE, null);
    return result.singleNodeValue ? result.singleNodeValue : null;
  }

  GM_xmlhttpRequest({
    method: 'get',
    url: 'http://wedata.net/databases/SearchForm/items.json',
    onload: function(response) {
      var data = eval(response.responseText);
      data.forEach(function(datum) {
        var url = datum['data']['url'];
        if(location.href.match(url)) {
          searchform = datum['data']['form'];
        }
      });
    }
  });
})();