可见性
隐藏对象没有宽高，前提是用display:none处理的
jQuery.expr.filters.hidden = function( elem ) {
// Support: Opera <= 12.12
// Opera reports offsetWidths and offsetHeights less than zero on some elements
return elem.offsetWidth <= 0 && elem.offsetHeight <= 0;
};
jQuery.expr.filters.visible = function( elem ) {
return !jQuery.expr.filters.hidden( elem );
};内容
获取文本内容通过indexOf匹配
"contains": markFunction(function( text ) {
return function( elem ) {
return ( elem.textContent || elem.innerText || getText( elem ) ).indexOf( text ) > -1;
};
}),取空
递归这个节点，排除nodeType大于6的节点
// Contents
"empty": function( elem ) {
// http://www.w3.org/TR/selectors/#empty-pseudo
// :empty is negated by element (1) or content nodes (text: 3; cdata: 4; entity ref: 5),
// but not by others (comment: 8; processing instruction: 7; etc.)
// nodeType < 6 works because attributes (2) do not appear as children
for ( elem = elem.firstChild; elem; elem = elem.nextSibling ) {
if ( elem.nodeType < 6 ) {
return false;
}
}
return true;
},
查看包含
递归sizzle通过传递上下文对象，实现包含查找
"has": markFunction(function( selector ) {
return function( elem ) {
return Sizzle( selector, elem ).length > 0;
};
}),匹配含有子元素或者文本的元素
"parent": function( elem ) {
return !Expr.pseudos["empty"]( elem );
},