Get this: week, month and year range Date prototype

definitions.js

Date.prototype.getThisWeek = function () {
  var y = this.getFullYear(),
      m = this.getMonth(),
      f = this.getDate() - this.getDay(),
      l = f + 6;

  return [new Date(y, m, f), new Date(y, m, l)];
};

Date.prototype.getThisMonth = function () {
	var y = this.getFullYear(),
			m = this.getMonth();

	return [new Date(y, m, 1), new Date(y, m + 1, 0)];
};

Date.prototype.getThisYear = function () {
	var y = this.getFullYear();

	return [new Date(y, 0, 0), new Date(y + 1, 0, 0)];
};

usage.js

window.selectedTimeRange = (selTimeRange === 'this week') ?
  new Date().getThisWeek() : (selTimeRange === 'this month') ?
  new Date().getThisMonth() : new Date().getThisYear();