//p = console.log;

$(function(){
  var conf = {
    className : 'btn',
    postfix : '_on'
  };
  $('.'+conf.className).each(function(){
    this.originalSrc = this.src;
    this.rolloverSrc = this.originalSrc.replace(/(_[a-z]{2})?(\.gif|\.jpg|\.png)/, conf.postfix+"$1$2");
    if (!this.src.match('btn_right\.gif$')) {
    	preloadImage(this.rolloverSrc);
    }
  }).hover(function(){
    if (this.src.match('btn_right\.gif$')) {
    	this.src = this.originalSrc;
    } else {
	    this.src = this.rolloverSrc;
	}
  },function(){
    this.src = this.originalSrc;
  });
});

//プリロード
preloadedImages = [];
function preloadImage(url){
	var p = preloadedImages;
	var l = p.length;
	p[l] = new Image();
	p[l].src = url;
}