difference between jQuery.live and jQuery.delegate_问答_开发者

I have read some post about why do not use jQuery.live() and I want to check if I got it:) When I call $("body").delegate('element','click', function);

Is it the same as $(element).live('click', function) ? In case of normal behaviour..According to the post there are some stopPropagation and performanc开发者_开发问答e boons, but is the main difference that live bind everytime to body element, while delegate can bind to another one?

One important difference is that ".live()" will actually build up the jQuery element list for the initial selector, even though the ".live()" function itself only needs the selector string. That means that if the selector is somewhat expensive, the code to set up the handler will go running all over the DOM for no good reason. The ".delegate()" call does not do that.

Really I don't see any reason that new code should use ".live()"; it was sort-of an architectural mistake and should eventually die quietly.

Nettuts has a screencast just to explain this: Quick Tip: The Difference Between Live() and Delegate()

Quote from the site:

// Live(), introduced in 1.3, allows for the binding  
// of event handlers to all elements that match a  
// selector, including those created in the future.  
// It does this by attaching the handler to the document.  
// Unfortunately, it does not work well with chaining.  
// Don't expect to chain live() after calls like  
// children().next()...etc.  
$("li").live("click", function() {  
    $(this).parent().append("<li>New Element</li>");  
});   

// Delegate, new to version 1.4, perhaps should have been a complete  
// replacement for Live(). However, that obviously  
// would have broken a lot of code! Nonetheless,  
// delegate remedies many of the short-comings  
// found in live(). It attaches the event handler  
// directly to the context, rather than the document.  
// It also doesn't suffer from the chaining issues  
// that live does. There are many performance benefits  
// to using this method over live().  
$('#items').delegate('li', 'click', function() {  
    $(this).parent().append('<li>New Element</li>');  
});

is the main difference that live bind everytime to body element, while delegate can bind to another one?

Yes, exactly. Let's say you have a table that you add and remove rows from, and you want to handle clicks on those rows (or links or buttons within the rows). You could use live for that, but then the event has to bubble all the way down to the body level and let's face it, it feels a bit like a global variable. If you use delegate on the table element instead, you remain more targeted, isolated from other things going on on the page. delegate is a more modular, contained version of live.

Since the .live() method handles events once they have propagated to the top of the document, it is not possible to stop propagation of live events. Similarly, events handled by .delegate() will always propagate to the element to which they are delegated; event handlers on any elements below it will already have been executed by the time the delegated event handler is called.

The short of it is that .live runs at the document level and .delegate runs on whatever element you specify. Why does it make a difference? If you have a mousemove event (or several) bound using .live, jQuery will execute code every time you move your mouse anywhere on the page to see if your callback function should run. This is extremely inefficient and is the reason for having .delegate. .delegate functions only run when the even originates inside of the dom node you specify. If, for example, you said $('ul#myUL').delegate(...), then jQuery would only check to see if the code should run when the event originated from within ul#myUL