jquery - 启用按钮令人困惑

Question

我总是尝试这样做 $("input[name=button]").attr("disabled", ''); 但它不起作用。为什么这不起作用？

我最终使用了这个$("input[name=button]").attr("disabled", false);。在我看来，两者是等效的。

Answer 1

Why does this not work?

disabled 是所谓的 boolean attribute :

A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.

因此空值仍然表示该属性的存在，因此表单元素保持禁用状态。

<小时/>

Seems to me that both are equivalent.

他们不是。 jQuery 以不同的方式处理 bool 属性。它测试新的值，呃，值，和 removes the attribute if the value is false :

set: function( elem, value, name ) {
    var propName;
    if ( value === false ) {
        // Remove boolean attributes when set to false
        jQuery.removeAttr( elem, name );
    } else {
        // ...
    }
    return name;
}