Search with google

// ==UserScript==
// @name         Search site with google
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       Kotique
// @match        *food4vita.ru*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var searchField = document.getElementById('searchfrm');
    searchField.addEventListener('keypress', function (event) {
        if (event.keyCode !== 13) { return; }
        var redirectUrl = 'https://www.google.com/search?q=' + encodeURIComponent(event.target.value) + ' site:food4vita.ru';
        console.log(redirectUrl);
        window.location.href = redirectUrl;
    });
})();