.attr() does not return "undefined" in IE6/7 for an undefined attribute

[Beeper]

On an input-element i want to check an attribute for existence. so i have something like: $('#id').attr('src') !== undefined

Here is the working example for Jquery 1.3.2: ​http://jsbin.com/oveci

Here is the Bug: ​http://jsbin.com/oveci/3

It seems to apply only for some HTML-Elements. I tried 'p' and .attr works fine, but for input-elements it returns "" and not "undefined".

[dmethvin]

For attributes that mirror properties on specific DOM elements, such as the checked attribute on a checkbox or radio button, .attr() will return a non-undefined value.

The best cross-browser way to approach this is to check for a falsy value using if ( $('#id').attr('src') ) rather than checking for a particular value.

[Rick Waldron]

This is not a bug, please see post by dmethvin

[addyosmani]

Docs updated: ​http://api.jquery.com/attr/