はてなブログで日付に曜日を付けるやつ (1行版もあります。)

hatenablog-date-to-week.js

(function(){
	datetimeEle = document.querySelectorAll('.date [datetime]');
	for (var i = 0; i < datetimeEle.length; i++){
		datetimeEle[i].appendChild(DateToWeek(datetimeEle[i].getAttribute("datetime")));
	}
	function DateToWeek(day){
		if(typeof day === "undefined"){return ""}
		//day = day.substr(0,10);
		var d = new Date(day);
		if(typeof d === "undefined" || isNaN( d ) ){return ""}
		var w = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"];
/*
		var w = ["日","月","火","水","木","金","土"];
*/
		var el = document.createElement("span");
		var str = document.createTextNode(w[d.getDay()]);
		el.setAttribute("class", "date-week date-week-" + str.data);
		el.appendChild(str);
		return el;
	}
})();

これは何ですか？： http://psn.hatenablog.jp/entry/2014/03/02/112020
もっと簡単にできませんか？：http://psn.hatenablog.jp/entry/2014/03/30/225710