DOM
记住每个DOM节点都有5个指针(属性)：parentNode previousSibling nextSibling fistChild lastChild.DOM指针不仅可以指向元素，也可以指向文本节点。XML存在一个有争议的地方：空格。在Firefox中把空格看做是一个文本节点。所以使用这些指针不能兼容浏览器。
1、处理DOM中的空格
// If no element is provided, do the whole HTML document
element = element || document;
// Use the first child as a starting point
var cur = element.firstChild;
// Go until there are no more child nodes
while ( cur != null ) {
// If the node is a text node, and it contains nothing but whitespace
// \S 表示任何非空白字符
if ( cur.nodeType == 3 && ! /\S/.test(cur.nodeValue) ) {
// Remove the text node
element.removeChild( cur );
// Otherwise, if it’s an element
} else if ( cur.nodeType == 1 ) {
// Recurse down through the document
cleanWhitespace( cur );
}
cur
= cur.nextSibling; // Move through the child nodes}
}
节点的类型可以由检查它的nodeType属性来确定。一般使用如下3个值：
nodeType=1 匹配元素
nodeType=3 匹配文本
nodeType=9 匹配文档的根元素
2、简单的DOM遍历
do {
elem = elem.previousSibling;
} while ( elem && elem.nodeType != 1 );
return elem;
}
function next( elem ) {
do {
elem = elem.nextSibling;
} while ( elem && elem.nodeType != 1 );
return elem;
}
function first( elem ) {
elem = elem.firstChild;
return elem && elem.nodeType != 1 ?
nextSibling( elem ) : elem;
}
function last( elem ) {
elem = elem.lastChild;
return elem && elem.nodeType != 1 ?
prevSibling( elem ) : elem;
}
function parent( elem, num ) {
num = num || 1;
for ( var i = 0; i < num; i++ )
if ( elem != null ) elem = elem.parentNode;
return elem;
}
