jQuery memoization, of sorts. WIP UNTESTED

jquery.ba-simple-cache.js

/*!
 * $imple cache - v0.3pre - 07/16/2010
 * http://benalman.com/
 * 
 * Copyright (c) 2010 "Cowboy" Ben Alman
 * Dual licensed under the MIT and GPL licenses.
 * http://benalman.com/about/license/
 */

(function($,window){
  '$:nomunge'; // Used by YUI compressor.
  
  // Element cache.
  var cache = {},
    
    // Element expando + unique ID for caching.
    expando = '$implecache' + +new Date(),
    guid = 0,
    
    // A reference to the original method.
    orig_init = $.fn.init;
  
  $.fn.init = function( selector, context, use_cache ) {
    var result,
      key,
      id;
    
    // `context` arg wasn't passed, but `use_cache` was.
    if ( typeof context === 'boolean' ) {
      use_cache = context;
      context = undefined;
    }
    
    // Use cache.
    if ( typeof use_cache === 'boolean' ) {
      // Generate a unique id from the passed selector and/or context.
      key = $.trim( get_key( context ) + ' ' + get_key( selector ) );
      
      // If `use_cache` is true and the cache is populated, return that.
      if ( use_cache && cache[ key ] ) {
        return cache[ key ];
      }
    }
    
    // Call the original $.fn.init method with selector and context.
    result = new orig_init( selector, context );
    
    // Since the cache is being used, update it for next time.
    if ( key ) {
      cache[ key ] = result;
    }
    
    return result;
  };
  
  // This logic probably needs to be improved a bit.
  function get_key( val ) {
    var result,
      id;
    
    if ( val === undefined ) {
      result = '';
      
    } else if ( typeof val === 'string' ) {
      result = val;
      
    } else if ( val && val.hasOwnProperty && val instanceof jQuery ) {
      result = val.selector;
      
    } else {
      id = val[ expando ] || ( val[ expando ] = ++guid );
      result = expando + id;
    }
    
    return result;
  };
  
})(jQuery,this);