inspired by monday.vim

monday.js

/**
 * @author <a href="mailto:[email protected]">MOGAMI Shu</a>
 */
(function(namespace){

	/** @private */
	var _map = {};

	// assign static function to monday
	monday["addAll"]  = addAll;
	monday["addPair"] = addPair;

	// export
	namespace["monday"] = monday;

	/**
	 * Get a successors/predecessors of a word from circulating words group.
	 * @param  {string} word
	 * @param  {number} [num=0] 
	 * @return {string} successor or predecessor of a word
	 * @example  monday("mon") === "tue"
	 * @example  monday("mon", 2) === "wed"
	 * @example  monday("mon", 7) === "mon"
	 * @example  monday("mon",-1) === "sun"
	 */
	function monday(word, num) {
		if (num == null) num = +1;
		if ((num|0) == 0) return word;
		if (_map.hasOwnProperty(word)) {
			if (num > 0) {
				var successor = _map[word];
				return monday(successor, num-1);
			} else {
				for (var pre in _map) if (_map.hasOwnProperty(pre)) {
					if (_map[pre] == word) {
						return monday(pre, num+1);
					} 
				}
			}
		}
		return ""; // not found
	}

	/**
	 * Make circulating word by chaining all parameters.
	 * @param {...string} var_args
	 * @example addAll("spring","summer","fall","winter")
	 */
	function addAll(var_args) {
		var args = arguments,
			i=0,
			iz=args.length;
		while(i<iz) {
			addPair(args[i], args[++i]);
		}
		addPair(args[iz-1], args[0]); // connect last to first
	}

	/**
	 * Add the word pair (successor/predecessor)
	 * @param  {string} successor
	 * @param  {string} predecessor
	 */
	function addPair(successor, predecessor) {
		_map[successor] = predecessor;
	}

	// days abbreviation
	addAll("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun");
	addAll("mon", "tue", "wed", "thu", "fri", "sat", "sun");
	addAll("MON", "TUE", "WED", "THU", "FRI", "SAT", "SUN");

	// days full
	addAll("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday");
	addAll("monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday");
	addAll("MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY", "SUNDAY");

	// months abbreviation
	addAll("Jan","Feb","Mar","Apr","May", "Jun", "Jul","Aug","Sep", "Oct", "Nov", "Dec"); // May -> June
	addAll("jan","feb","mar","apr","may", "jun", "jul","aug","sep", "oct", "nov", "dec"); // may -> june
	addAll("JAN","FEB","MAR","APR","MAY", "JUN", "JUL","AUG","SEP", "OCT", "NOV", "DEC"); // MAY -> JUNE

	// months full
	addAll("January","February","March","April","May", "June", "July","August","September", "October", "November", "December");
	addAll("january","february","march","april","may", "june", "july","august","september", "october", "november", "december");
	addAll("JANUARY","FEBRUARY","MARCH","APRIL","MAY", "JUNE", "JULY","AUGUST","SEPTEMBER", "OCTOBER", "NOVEMBER", "DECEMBER");

	// two alternatives
	addAll("true","false");
	addAll("yes","no");
	addAll("on","off");

})(window || this);