gistfile1.js

// 一番最初に実行する
window.sessionStorage.setItem('total', 0);

// ♪ここから

// load
var total = parseInt(window.sessionStorage.getItem('total'), 10);

// totaling
total += (function () {
  var total = 0;
	
	var prices = document.getElementsByClassName('price');
	
	for (var i = 0; prices.length > i; i++) {
		total += parseInt(prices[i].innerText.replace('￥ ', '').replace(',', ''));
	}
	
	return total;
})();

// save
window.sessionStorage.setItem('total', total);

// 合計の表示
total;

// 次のページへ（あれば）飛ぶ
var navs = document.getElementsByClassName('num-pages');

for (var i = 0; navs.length > i; i++) {
	var links = navs[i].getElementsByTagName('a');
	
	for (var j = 0; links.length > j; j++) {
		if (links[j].innerText == '次へ »') {
			window.location.href = links[j].href;
		}
	}
}

// ♪繰り返し