jQuery1.11源码分析，8-----jQuery调用Sizzle引擎的相关API

之所以把这部分放在这里，是因为这里用到了一些基本API，前一篇介绍过后才能使用。

//jQuery通过find方法调用Sizzle引擎
//jQuery通过find方法调用Sizzle引擎
jQuery.find = Sizzle;
jQuery.expr = Sizzle.selectors;
jQuery.expr[":"] = jQuery.expr.pseudos;
jQuery.unique = Sizzle.uniqueSort;
jQuery.text = Sizzle.getText;
jQuery.isXMLDoc = Sizzle.isXML;
jQuery.contains = Sizzle.contains;



var rneedsContext = jQuery.expr.match.needsContext;

//匹配没有其他如class等任何属性的标签，就是简单标签，
//如<input />和<div></div>
var rsingleTag = (/^<(\w+)\s*\/?>(?:<\/\1>|)$/);


//当selector为 .header这样的形式则为简单选择符
var risSimple = /^.[^:#\[\.,]*$/;

// Implement the identical functionality for filter and not
//比较难啃的一个函数，传入参数有几种用法。后面的多个过滤函数都依赖于这个函数
//第一个参数表示element元素集，第二个参数传入过滤函数、DOM、选择符、数组，第三个参数为预设结果
function winnow( elements, qualifier, not ) {
        if ( jQuery.isFunction( qualifier ) ) {
                return jQuery.grep( elements, function( elem, i ) {
                        /* jshint -W018 */
                        return !!qualifier.call( elem, i, elem ) !== not;
                });

        }

        if ( qualifier.nodeType ) {
                return jQuery.grep( elements, function( elem ) {
                        return ( elem === qualifier ) !== not;
                });

        }

        if ( typeof qualifier === "string" ) {
                if ( risSimple.test( qualifier ) ) {
                        return jQuery.filter( qualifier, elements, not );
                }

                qualifier = jQuery.filter( qualifier, elements );
        }

        return jQuery.grep( elements, function( elem ) {
                return ( jQuery.inArray( elem, qualifier ) >= 0 ) !== not;
        });
}

//过滤函数
jQuery.filter = function( expr, elems, not ) {
        var elem = elems[ 0 ];

        if ( not ) {
                expr = ":not(" + expr + ")";
        }
    //其实这两个区别不大，都要调用Sizzle
        return elems.length === 1 && elem.nodeType === 1 ?
                jQuery.find.matchesSelector( elem, expr ) ? [ elem ] : [] :
                jQuery.find.matches( expr, jQuery.grep( elems, function( elem ) {
                        return elem.nodeType === 1;
                }));
};

//开始jQuery对象的原型进行扩展
jQuery.fn.extend({
        find: function( selector ) {

                var i,
                        ret = [],
                        self = this,
                        len = self.length;
        //当传入的参数是字符串类型时，调用下面的filter方法，本质是调用上面的winnow，winnow里又视情况调用sizzle
                if ( typeof selector !== "string" ) {
                        return this.pushStack( jQuery( selector ).filter(function() {
                console.log('find');
                console.log(self);
                                for ( i = 0; i < len; i++ ) {
                    //如果self包含符合selector的this，注意这里的this是新的jQuery对象
                                        if ( jQuery.contains( self[ i ], this ) ) {
                                                return true;
                                        }
                                }
                        }) );
                }
        //否则以self[i]为查找上下文context进行查找
                for ( i = 0; i < len; i++ ) {
                        jQuery.find( selector, self[ i ], ret );
                }

                // Needed because $( selector, context ) becomes $( context ).find( selector )
        //这里是正常的压栈和选择符拼接
                ret = this.pushStack( len > 1 ? jQuery.unique( ret ) : ret );
                ret.selector = this.selector ? this.selector + " " + selector : selector;
                return ret;
        },
        filter: function( selector ) {
                return this.pushStack( winnow(this, selector || [], false) );
        },
        not: function( selector ) {
                return this.pushStack( winnow(this, selector || [], true) );
        },
        is: function( selector ) {
        //通过winnow返回的长度来判断
                return !!winnow(
                        this,

                        // If this is a positional/relative selector, check membership in the returned set
                        // so $("p:first").is("p:last") won't return true for a doc with two "p".
                        typeof selector === "string" && rneedsContext.test( selector ) ?
                                jQuery( selector ) :
                                selector || [],
                        false
                ).length;
        }
});