Live Query utilizes the power of jQuery selectors by firing callbacks for matched elements auto-magically, even after the page has been loaded and the DOM updated.

Live Query fires a function (callback) when it matches a new element and another function (callback) for when an element is no longer matched. This provides ultimate flexibility and untold use-cases. For example the following code uses a function based Live Query to implement the jQuery hover helper method and remove it when the element is no longer matched.

$('li') 
    .livequery(function(){ 
    // use the helper function hover to bind a mouseover and mouseout event 
        $(this) 
            .hover(function() { 
                $(this).addClass('hover'); 
            }, function() { 
                $(this).removeClass('hover'); 
            }); 
    }, function() { 
        // unbind the mouseover and mouseout events 
        $(this) 
            .unbind('mouseover') 
            .unbind('mouseout'); 
    }); 

The livequery method has 2 different signatures or ways to call it.

Pass one or two functions to livequery. Doing this, livequery will call the first passed function when an element is newly matched and will call the second passed function when an element is removed or no longer matched. The second function is optional. The this or context of the first function will be the newly matched element. For the second function it will be the element that is no longer matched.

// matchedFn: the function to execute when a new element is matched
$(selector).livequery( matchedFn );

// matchedFn: the function to execute when a new element is matched
// unmatchedFn: the function to execute when an element is no longer matched
$(selector).livequery( matchedFn, unmatchFn );

The expire method has 3 different signatures or ways to call it.

The first way will stop/expire all live queries associated with the selector.

$(selector).expire();

The second way will stop/expire all live queries associated with the selector and matchedFn.

// matchedFn: the function to execute when a new element is matched
$(selector).expire( matchedFn );

The third way will stop/expire all live queries associated with the selector, matchedFn, and unmatchedFn.

// matchedFn: the function to execute when a new element is matched
// unmatchedFn: the function to execute when an element is no longer matched
$(selector).expire( matchedFn, unmatchFn );

If your plugin modifies the DOM without using the built-in DOM Modification methods (append, addClass, etc), you can register your plugin with Live Query like this.

if (jQuery.livequery) 
    jQuery.livequery.registerPlugin("pluginMethodName"); 

You can register several plugin methods at once by just passing them as additional arguments to the registerPlugin method.

if (jQuery.livequery) 
    jQuery.livequery.registerPlugin("method1", "method2", "method3"); 

The Live Query plugin is dual licensed (just like jQuery) under the MIT (MIT_LICENSE.txt) and GPL Version 2 (GPL_LICENSE.txt) licenses.

Copyright (c) 2010 Brandon Aaron (c) 2012 Alexander Zaytsev (c) 2013 Frank Förster