A commonly requested feature that is simply not worth adding to jQuery core. Usage: http://jsfiddle.net/rwaldron/kSmP2/

jquery.hasattr.js

/*!
 * jQuery.fn.hasAttr()
 *
 * Copyright 2011, Rick Waldron
 * Licensed under MIT license.
 *
 */
(function( jQuery ) {
  jQuery.fn.hasAttr = function( name ) {
      for ( var i = 0, l = this.length; i < l; i++ ) {
          if ( !!( this.attr( name ) !== undefined ) ) {
              return true;
          }
      }
      return false;
  };
})( jQuery );

tests.js

function assert( actual, expected, msg ) {
    console.log(  
        ( actual === expected && "PASS" ) || "FAIL: actual: " + actual + ", expected: " + expected, 
        msg
    );
}

var $div = $("div");


assert( $div.hasAttr("class"), true, "class === 'foo'" );
assert( $div.hasAttr("title"), true, "title attr === 0" );
assert( $div.hasAttr("alt"), false, "alt attr === false" );