jQuery - own methods

chil-of-selector.js

$(function(){
	jQuery.extend(jQuery.expr[':'], {   
		'child-of' : function(a,b,c) {
			return (jQuery(a).parents(c[3]).length > 0);
		}   
	});
 
	//'child-of' is now a valid selector:
	$("li:child-of(ul.test)").css("background","#000");  
});

is-child-of.js

$(function(){
	jQuery.fn.isChildOf = function(b){return (this.parents(b).length > 0);};
 
	//Now we can evaluate like this:
	if ( $("li").isChildOf("ul") ){
		//Obviously, the li is a child of the ul so this code is executed
	}
});

jquery-own-methods.js

$(function(){
	jQuery.fn.putBefore = function(dest){
		return this.each(function(){
			$(dest).before($(this));
		});
	}
	jQuery.fn.putAfter = function(dest){
		return this.each(function(){
			$(dest).after($(this));
		});
	}
});