Test jQuery version WIP UNTESTED

jquery.ba-isversion.js

/*!
 * jQuery isVersion - v0.1 - 07/02/2010
 * http://benalman.com/
 * 
 * Copyright (c) 2010 "Cowboy" Ben Alman
 * Dual licensed under the MIT and GPL licenses.
 * http://benalman.com/about/license/
 */

(function($){
  '$:nomunge'; // Used by YUI compressor.
  
  var re = /^([!<>=]+)?\s*((\d+(?:\.\d+)*)(pre)?)$/i,
    cur = get_num( $.fn.jquery || '' );
  
  // Return true if all version criteria are met. Comparison operator defaults
  // to == if omitted. Valid comparisons are == != < <= > >=.
  // 
  // ie. $.isVersion( '1.3.2' ) or $.isVersion( '>= 1.4', '!= 1.4.1' )
  // 
  $.isVersion = function() {
    var result;
    
    // Iterate over all function arguments, allowing any number of tests.
    $.each( arguments, function(i,v){
      var matches = v.match( re );
      
      // If the regexp matched, then evaluate the comparison, setting `result`
      // to that value, and returing it (so that a `false` value will break
      // out of the each loop).
      return matches && ( result = (new Function(
        'return ' + cur + ( matches[1] || '==' ) + get_num( matches[2] )
      ))() );
    });
    
    return result;
  };
  
  // Get number that can be used for comparison. Converts a string like
  // "1.2.3.4" into the number 1020304 (and "1.2.3.4pre" into the number
  // 1020303.9) for easy numeric comparisons.
  function get_num( str ) {
    var matches = str.match( re ),
      num = 0;
    
    if ( matches ) {
      $.each( matches[3].split('.'), function(i,v){
        num += Math.pow( 0.01, i ) * v * 1000000;
      });
      
      num -= matches[4] ? 0.1 : 0;
    }
    
    return num;
  };
  
})(jQuery);

That's incorrect, eval has some limitations such as using the same ThisBinding, LexicalEnvironment, and VariableEnvironment as the calling execution context. There are also further restrictions placed on eval in ES5's strict mode.

ES5 tries to fix eval but ES3 is still the reality.

Furthermore, large use of eval, the Function constructor, or script injection will minify less because they all use strings.

I was not pointing on the problem of minifing strings, but on the incapacity to compress names declared in all parent scopes of the one with the eval. Function, in other hand, has not this issue because it evaluates script globally.

ES5 tries to fix eval but ES3 is still the reality.

Sure but at least there are more restrictions coming soon (Firefox 4).
The same can't be said for script injection.

I was not pointing on the problem of minifing strings, but on the incapacity to compress names declared in all parent scopes of the one with the eval.

True, but it comes down to how you use it. The same could be said for the Function constructor if your code accesses pseudo private properties/methods on a global object (those prefixed with an underscore _) because some minifiers will shrink them.