Ajax auto-cache

ajaxCache.example.js

 var aCache = new ajaxCache({pk: "folder_id", prefix: "folder");

$('#folder_sel').change(function() {
  var folder_id = $(this).val();
  aCache.post(href_val, {'folder_id': folder_id}, function(data) {
	  //code
  });
})

ajaxCache.js

var ajaxCache = function(cfg){
	this._cache  = {};
	this._pk     = cfg.pk||null;
	this._prefix = cfg.prefix||'';
};

ajaxCache.prototype = {
    constructor: ajaxCache,

    set: function(key, val) {
    	this._cache[key] = val;
    },

    get: function(key) {
    	return this.exists(key) ? this._cache[key] : null;
    },

    exists: function(key) {
    	return key in this._cache;
    },

	fetch: function(method, url, data, callback, type) {
		if ( $.isFunction( data ) )
		{
			type     = type || callback;
			callback = data;
			data     = undefined;
		}
		var self = this
			key  = this._pk ? this._pk+':'+data[this._pk] : url;
		 	key  = this._prefix + key;
		
		
		if (this.exists(key))
		{
			return callback.call(this, self.get(key));
		}
		return $.ajax({
			url: url,
			type: method,
			dataType: type,
			data: data,
			success: function(data) {
				self.set(key, data);
				callback.call(this, data);
			}
		});
	},
	load: function(url, data, callback, type) {
		this.fetch('get', url, data, callback, type );
	},
	post: function(url, data, callback, type) {
		this.fetch('post', url, data, callback, type );
	}
};