Dynamically Including jQuery using JavaScript if it's not already present

Answer 1

function doMyStuff(jQueryJustForThisFn) {
    // do jQuery stuff!
    jQueryJustForThisFn('div').addClass('wow');
}

function check() {
    return window.jQuery && jQuery.fn && /^1\.[3-9]/.test(jQuery.fn.jquery);
}

if ( check() ) {

    doMyStuff( jQuery );

} else {

    var script = document.createElement('script'),

        timer = setInterval(function(){
            if ( check() ) {
                clearInterval(timer);
                document.body.removeChild(script);
                doMyStuff( jQuery.noConflict(true) );
            }
        }, 30);

    script.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js';

    document.body.insertBefore( script, document.body.firstChild );

}

Answer 2

I don't know much about the noConflict, so i can only mostly answer 2.

This is usually called lazy loading. See my answer on a similar question to do this

Answer 3

I haven't tried to see how it behaves with a lower-version already loaded, but you may want to check out google.load

http://code.google.com/apis/ajaxlibs/documentation/#googleDotLoad

Answer 4

For absolute safety, you may want to consider namespacing the version of jQuery you are using. It's a bit ugly, but a regex against the codebase to define your own global attach point will ensure you break nothing. If the code will be widely deployed across a variety of sites, this will be your best option and most ensure future compatibility.

Answer 5

(function(){

    var myBkl = {
             jq: null,
             loadScript: function(src) {
                    if(window.jQuery && window.jQuery.fn.jquery == '1.3.2'){
                            return;
                    }
                    var s = document.createElement('script');
                    s.setAttribute('src', src);
                    s.setAttribute('type', 'text/javascript');
                    document.getElementsByTagName('head')[0].appendChild(s); 
            },
            whenLoaded: function(callback){
                    if (typeof(window.jQuery) !== 'undefined' && window.jQuery.fn.jquery == '1.3.2') { 
                            myBkl.jq = window.jQuery.noConflict(true);
                            callback(myBkl.jq); 
                    } 
                    else {
                            setTimeout((function() {myBkl.whenLoaded(callback); }), 100);
                    } 
            },
            init: function($){
                    console.log($.fn.jquery);
                    console.log(window.jQuery.fn.jquery);
            }
    };
    myBkl.loadScript('http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.js');
    myBkl.whenLoaded(myBkl.init);

})();