jQuery中的traversing查找及遍历

jQuery提供了一整套非常好用的遍历Dom树节点的API，下面是看源码的过程，看完了后对API进行分级别，将将要的级别移到插件，或者将其删除，保持jQuery的精简。

学习重点：
正则表达式深化

var rparentsprev = /^(?:parents|prevUntil|prevAll)/;

     ?:在正则表达式中表示：非捕获子模式，即使满足parents|prevUntil|prevAll，也不捕获

同类方法的抽取
    parent，parents...，并将他们推入栈中（pushStack），回顾pushStack方法定义在core.js中，方法中通过链接的方式设置了一个preObject属性，为end()方法留下可能。

(function( jQuery ) {
 // ?:在正则表达式中表示：非捕获子模式，即使满足parents|prevUntil|prevAll，也不捕获
 // /,/用于多个选择器分隔
 //
var runtil = /Until$/,
	rparentsprev = /^(?:parents|prevUntil|prevAll)/,
	// Note: This RegExp should be improved, or likely pulled from Sizzle
	rmultiselector = /,/,
	// 以任何字符开始，并且后续字符是非# [ . ,的正则表达式
	isSimple = /^.[^:#\[\.,]*$/,
	slice = Array.prototype.slice,
	POS = jQuery.expr.match.globalPOS,
	// methods guaranteed to produce a unique set when starting from a unique set
	guaranteedUnique = {
		children: true,
		contents: true,
		next: true,
		prev: true
	};

jQuery.fn.extend({
	find: function( selector ) {
		var self = this,
			i, l;
		//如果是简单的字符串，则交由filter函数，通过contains函数判断是否需要过滤掉集合同的数据（其中contains方法在sizzle中）
		if ( typeof selector !== "string" ) {
			return jQuery( selector ).filter(function() {
				for ( i = 0, l = self.length; i  0 ) {
				// Make sure that the results are unique
				for ( n = length; n = 0 :
					jQuery.filter( selector, this ).length > 0 :
				this.filter( selector ).length > 0 );
	},

	// TODO：这个API可以删除，最近的元素
	closest: function( selectors, context ) {
		var ret = [], i, l, cur = this[0];

		// Array (deprecated as of jQuery 1.7)
		if ( jQuery.isArray( selectors ) ) {
			var level = 1;

			while ( cur && cur.ownerDocument && cur !== context ) {
				for ( i = 0; i  -1 : jQuery.find.matchesSelector(cur, selectors) ) {
					ret.push( cur );
					break;

				} else {
					cur = cur.parentNode;
					if ( !cur || !cur.ownerDocument || cur === context || cur.nodeType === 11 ) {
						break;
					}
				}
			}
		}

		ret = ret.length > 1 ? jQuery.unique( ret ) : ret;

		return this.pushStack( ret, "closest", selectors );
	},

	// Determine the position of an element within
	// the matched set of elements
	// 获取元素的索引
	index: function( elem ) {

		// No argument, return index in parent
		if ( !elem ) {
			return ( this[0] && this[0].parentNode ) ? this.prevAll().length : -1;
		}

		// index in selector
		if ( typeof elem === "string" ) {
			return jQuery.inArray( this[0], jQuery( elem ) );
		}

		// Locate the position of the desired element
		return jQuery.inArray(
			// If it receives a jQuery object, the first element is used
			elem.jquery ? elem[0] : elem, this );
	},

	// 将元素添加进来
	add: function( selector, context ) {
	    // 对selector进行简单的判断
		var set = typeof selector === "string" ?
				jQuery( selector, context ) :
				jQuery.makeArray( selector && selector.nodeType ? [ selector ] : selector ),
			all = jQuery.merge( this.get(), set );

				
		return this.pushStack( isDisconnected( set[0] ) || isDisconnected( all[0] ) ?
			all :
			jQuery.unique( all ) );
	},

	andSelf: function() {
		return this.add( this.prevObject );
	}
});

// A painfully simple check to see if an element is disconnected
// from a document (should be improved, where feasible).
function isDisconnected( node ) {
	return !node || !node.parentNode || node.parentNode.nodeType === 11;
}
// 对同类结果组合改变的API进行统一的抽象
jQuery.each({
    // 获取单个父结点
	parent: function( elem ) {
		var parent = elem.parentNode;
		return parent && parent.nodeType !== 11 ? parent : null;
	},
	// 获取所有父结点
	parents: function( elem ) {
		return jQuery.dir( elem, "parentNode" );
	},
	parentsUntil: function( elem, i, until ) {
		return jQuery.dir( elem, "parentNode", until );
	},
	next: function( elem ) {
		return jQuery.nth( elem, 2, "nextSibling" );
	},
	prev: function( elem ) {
		return jQuery.nth( elem, 2, "previousSibling" );
	},
	nextAll: function( elem ) {
		return jQuery.dir( elem, "nextSibling" );
	},
	prevAll: function( elem ) {
		return jQuery.dir( elem, "previousSibling" );
	},
	nextUntil: function( elem, i, until ) {
		return jQuery.dir( elem, "nextSibling", until );
	},
	prevUntil: function( elem, i, until ) {
		return jQuery.dir( elem, "previousSibling", until );
	},
	siblings: function( elem ) {
		return jQuery.sibling( ( elem.parentNode || {} ).firstChild, elem );
	},
	children: function( elem ) {
		return jQuery.sibling( elem.firstChild );
	},
	contents: function( elem ) {
		return jQuery.nodeName( elem, "iframe" ) ?
			elem.contentDocument || elem.contentWindow.document :
			jQuery.makeArray( elem.childNodes );
	}
}, function( name, fn ) {
	jQuery.fn[ name ] = function( until, selector ) {
		var ret = jQuery.map( this, fn, until );

		if ( !runtil.test( name ) ) {
			selector = until;
		}

		if ( selector && typeof selector === "string" ) {
			ret = jQuery.filter( selector, ret );
		}

		ret = this.length > 1 && !guaranteedUnique[ name ] ? jQuery.unique( ret ) : ret;

		if ( (this.length > 1 || rmultiselector.test( selector )) && rparentsprev.test( name ) ) {
			ret = ret.reverse();
		}

		return this.pushStack( ret, name, slice.call( arguments ).join(",") );
	};
});

jQuery.extend({
	filter: function( expr, elems, not ) {
		if ( not ) {
			expr = ":not(" + expr + ")";
		}
		// 完全是通过调用sizzle进行过滤，支持not表示“包含内”或者是“包含外”
		return elems.length === 1 ?
			jQuery.find.matchesSelector(elems[0], expr) ? [ elems[0] ] : [] :
			jQuery.find.matches(expr, elems);
	},

	// cur属于一个递归的调用过程，不断的将递归的结果放到cur里面，并添加到matched中，这个设计模式用得好
	dir: function( elem, dir, until ) {
		var matched = [],
			cur = elem[ dir ];

		while ( cur && cur.nodeType !== 9 && (until === undefined || cur.nodeType !== 1 || !jQuery( cur ).is( until )) ) {
			if ( cur.nodeType === 1 ) {
				matched.push( cur );
			}
			cur = cur[dir];
		}
		return matched;
	},

	// 获取第几个结点
	nth: function( cur, result, dir, elem ) {
		result = result || 1;
		var num = 0;

		for ( ; cur; cur = cur[dir] ) {
			if ( cur.nodeType === 1 && ++num === result ) {
				break;
			}
		}

		return cur;
	},

	// 递归获取兄弟结点，返回数组
	sibling: function( n, elem ) {
		var r = [];

		for ( ; n; n = n.nextSibling ) {
			if ( n.nodeType === 1 && n !== elem ) {
				r.push( n );
			}
		}

		return r;
	}
});

// Implement the identical functionality for filter and not
function winnow( elements, qualifier, keep ) {

	// Can't pass null or undefined to indexOf in Firefox 4
	// Set to 0 to skip string check
	qualifier = qualifier || 0;
	// grep函数在core.js中，若callback返回true，则elem保留
	// 如果qualifier为一个函数，则遍历elements，调用qualifier，若返回true，对象elem保留
	if ( jQuery.isFunction( qualifier ) ) {
		return jQuery.grep(elements, function( elem, i ) {
			var retVal = !!qualifier.call( elem, i, elem );
			return retVal === keep;
		});
	// 如果qualifier为一个dom结点，则直接比较elem比较
	} else if ( qualifier.nodeType ) {
		return jQuery.grep(elements, function( elem, i ) {
			return ( elem === qualifier ) === keep;
		});
	// 如果qualifier为string字符串，则
	} else if ( typeof qualifier === "string" ) {
		var filtered = jQuery.grep(elements, function( elem ) {
			return elem.nodeType === 1;
		});

		if ( isSimple.test( qualifier ) ) {
		    // 如果以任何字符开始，并且后续字符是非# [ . ,选择器，则直接返回使用sizzle过滤的结果，说明是单层级的
			return jQuery.filter(qualifier, filtered, !keep);
		} else {
		    // 其实这里的逻辑，加上下面的逻辑不就一样了吗？都是返回一个列表
			qualifier = jQuery.filter( qualifier, filtered );
		}
	}

	// 如果elem在qualifier中，则添加到结果中
	return jQuery.grep(elements, function( elem, i ) {
		return ( jQuery.inArray( elem, qualifier ) >= 0 ) === keep;
	});
}

})( jQuery );