判斷節點包含

• 元素包含

contains基本兼容
用法node.contains( otherNode )
compareDocumentPosition感受比較奇怪,聽說是這樣

The Node.compareDocumentPosition() method compares the position of the
current node against another node in any other document.
返回值分爲6個數字
jquery的selector-native有個原生方法contains這樣寫的

contains: function( a, b ) {
    var adown = a.nodeType === 9 ? a.documentElement : a, 
        bup = b && b.parentNode;
    return a === bup || !!( bup && bup.nodeType === 1 &&  adown.contains(bup) );
    }

比較容易理解

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update 2015-01-27

開發鳳凰焦點項目的時候，有用到判斷元素包含關係的contains,當時第一反應是想到jquery取子元素的方式.（以前看過實現方式的,忘了2333...）固然不是用的contains，由於相比取子元素更適合關係判斷.那麼jq是怎麼取的呢？

• node.nextSibling
• node.previousSibling
  沒錯，就是這倆屬性,traversing.js腳本可見

jQuery.extend({

    //direction
    dir: function( elem, dir, until ) {
        var matched = [],
            truncate = until !== undefined;

        while ( (elem = elem[ dir ]) && elem.nodeType !== 9 ) {
            if ( elem.nodeType === 1 ) {     //nodeType:1 --> element
                if ( truncate && jQuery( elem ).is( until ) ) {
                    break;
                }
                matched.push( elem );
            }
        }
        return matched;
    },
    
    sibling: function( n, elem ) {
        var matched = [];

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

        return matched;
    }
});

siblings: function( elem ) {
    return jQuery.sibling( ( elem.parentNode || {} ).firstChild, elem );
},
children: function( elem ) {
    return jQuery.sibling( elem.firstChild );
}