精通Javascript笔记

第五章中设置/获取元素属性的函数：

function attr(elem, name, value) {
    // Make sure that a valid name was provided
    if ( !name || name.constructor != String ) return '';

    // Figure out if the name is one of the weird naming cases
    name = { 'for': 'htmlFor', 'class': 'className' }[name] || name;

    // If the user is setting a value, also
    if ( value != null ) {
        // Set the quick way first
        elem[name] = value;
        
        // If we can, use setAttribute
        if ( elem.setAttribute )
           elem.setAttribute(name,value);
           
        
    }

    // Return the value of the attribute
    return elem[name] || elem.getAttribute(name) || '';
}
上述函数在设置元素属性，当元素属性为name范围中的值的时候，会为元素这个两个属性（例如"class"元素会有一个“className"属性和"class"属性，前者是由setAttribute设置，另一个为setter设置；

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In real life, in 98% of cases DOM properties are used.

You should use attributes in only two cases:

1. A custom HTML attribute, because it is not synced to DOM property.
2. To access a built-in HTML attribute, which is not synced from the property, and you are sure you need the attribute.
   For example, value in INPUT.

------http://javascript.info/tutorial/attributes-and-custom-properties

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所以基本上，我们使用"."可以解决大部分问题。不需要去使用标准高的DOM方法了。