Bookmarklet wait until Javascript is loaded

It depends on how you are actually loading jQuery. If you are appending a script element to the page, you can use the same technique that jQuery uses to dynamically load a script.

EDIT: I did my homework and actually extracted a loadScript function from the jQuery code to use in your bookmarklet. It might actually be useful to many (including me).

function loadScript(url, callback){    var head = document.getElementsByTagName("head")[0];    var script = document.createElement("script");    script.src = url;    // Attach handlers for all browsers    var done = false;    script.onload = script.onreadystatechange = function()    {        if( !done && ( !this.readyState                     || this.readyState == "loaded"                     || this.readyState == "complete") )        {            done = true;            // Continue your code            callback();            // Handle memory leak in IE            script.onload = script.onreadystatechange = null;            head.removeChild( script );        }    };    head.appendChild(script);}// Usage: // This code loads jQuery and executes some code when jQuery is loadedloadScript("https://code.jquery.com/jquery-latest.js", function(){    $('my_element').hide();});

To answer your first question: Javascript is interpreted sequentially, so any following bookmarklet code will not execute until the library is loaded (assuming the library was interpreted successfully - no syntax errors).

To prevent the files from being cached, you can append a meaningless query string...

url = 'jquery.js?x=' + new Date().getTime();

I've paid an attention that in Chrome the order of scripts that are loaded is undetermined, when using @Vincent Robert's technique. In this case a little modification helps:

(function() {    var callback = function() {        // Do you work    };        // check for our library existence    if (typeof (MyLib) == 'undefined') {        var sources = [                'http://ajax.cdnjs.com/ajax/libs/json2/20110223/json2.js',            'https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js',            'https://ajax.googleapis.com/ajax/libs/jqueryui/1.8.13/jquery-ui.min.js',            'http://myhost.com/javascripts/mylib.min.js'];        var loadNextScript = function() {            if (sources.length > 0) {                var script = document.createElement('script');                script.src = sources.shift();                document.body.appendChild(script);                var done = false;                script.onload = script.onreadystatechange = function() {                    if (!done                            && (!this.readyState || this.readyState == "loaded" || this.readyState == "complete")) {                        done = true;                        // Handle memory leak in IE                        script.onload = script.onreadystatechange = null;                        loadNextScript();                    }                }            } else {                callback();            }        }        loadNextScript();    } else {        callback();    }})();