sizzle分析记录：getAttribute和getAttributeNode

<form name="aaron">  
  <input type="text" name="aaron"/>  
</form>

alert(form.getAttribute('name')); IE6、7中错误

alert(form.getAttributeNode('name').nodeValue);

support.attributes = assert(function( div ) {
    div.className = "i"; //设置一个属性
    return !div.getAttribute("className");
});

Sizzle.attr = function( elem, name ) {

    return val !== undefined ?
        val :
        support.attributes || !documentIsHTML ?
            elem.getAttribute( name ) :
            (val = elem.getAttributeNode(name)) && val.specified ?
                val.value :
                null;
};