Code snippet to inject script to page, e.g. jquery. It can be used directly as bookmark in some browsers. (tested in chrome)

inject_script_to_page.js

javascript: (function() {

    var url = prompt('URL of script to inject:');

    if (url) {

        console.log('Script inject request URL:', url);

        var script = document.createElement('script');
        script.src = url;
        document.getElementsByTagName('head')[0].appendChild(script);

        console.log('Injected script: ', script);
    }

})();