Question

I always try to do this $("input[name=button]").attr("disabled", ''); and it doesn’t work. Why does this not work?

I ended up using this $("input[name=button]").attr("disabled", false);. Seems to me that both are equivalent.

Answer 1

Why does this not work?

disabled is a so called 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.

So an empty value still indicates the presence of the attribute and therefore the form element stays disabled.

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Seems to me that both are equivalent.

They are not. jQuery treats boolean attributes differently. It tests the value of the new, uhm, value, and 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;
}