jquery.datepicker.extension.range.min.js

/* jQuery ui-datepicker extension */

/**
 *
 * https://gist.github.com/Artemeey/8bacd37964a8069a2eeee8c9b0bd2e44/
 *
 * Version: 1.0 (15.06.2016)
 * Requires: jQuery v1.8+
 * Requires: jQuery-UI v1.10+
 *
 * Copyright (c) 2016 Artemeey
 * Under MIT and GPL licenses:
 *  http://www.opensource.org/licenses/mit-license.php
 *  http://www.gnu.org/licenses/gpl.html
 *
 * sample:
 * $('.datepicker').datepicker({
		range:'period', // 'period' or 'multiple'
		onSelect:function(dateText, inst, extensionRange){
			// range - new argument!
			switch(inst.settings.range){
				case 'period':
					console.log(extensionRange.startDateText);
					console.log(extensionRange.endDateText);
					console.log(extensionRange.startDate);
					console.log(extensionRange.endDate);
					break;
				case 'multiple':
					console.log(extensionRange.dates); // object, width UTC-TIME keys
					console.log(extensionRange.datesText); // object, width UTC-TIME keys
					break;
			}
		}
	});
 *
 * extension styles:
 * .selected
 * .selected-start
 * .selected-end
 * .first-of-month
 * .last-of-month
 *
 */
 
 $.datepicker._get_original=$.datepicker._get,$.datepicker._get=function(t,e){var i=$.datepicker._get_original(t,e),a=t.settings.range;if(!a)return i;var s=this;switch(a){case"period":case"multiple":var n=$(this.dpDiv).data("datepickerExtensionRange");switch(n||(n=new _datepickerExtension,$(this.dpDiv).data("datepickerExtensionRange",n)),n.range=a,n.range_multiple_max=t.settings.range_multiple_max||0,e){case"onSelect":var r=i;r||(r=function(){}),i=function(t,e){n.onSelect(t,e),r(t,e,n),s._datepickerShowing=!1,setTimeout(function(){s._updateDatepicker(e),s._datepickerShowing=!0}),n.setClassActive(e)};break;case"beforeShowDay":var r=i;r||(r=function(){return[!0,""]}),i=function(t){var e=r(t);return e=n.fillDay(t,e)};break;case"beforeShow":var r=i;r||(r=function(){}),i=function(t,e){r(t,e),n.setClassActive(e)};break;case"onChangeMonthYear":var r=i;r||(r=function(){}),i=function(t,e,i){r(t,e,i),n.setClassActive(i)}}}return i},$.datepicker._setDate_original=$.datepicker._setDate,$.datepicker._setDate=function(t,e,i){var a=t.settings.range;if(!a)return $.datepicker._setDate_original(t,e,i);var s=this.dpDiv.data("datepickerExtensionRange");if(!s)return $.datepicker._setDate_original(t,e,i);switch(a){case"period":("object"!=typeof e||void 0==e.length)&&(e=[e,e]),s.step=0,$.datepicker._setDate_original(t,e[0],i),s.startDate=this._getDate(t),s.startDateText=this._formatDate(t),$.datepicker._setDate_original(t,e[1],i),s.endDate=this._getDate(t),s.endDateText=this._formatDate(t),s.setClassActive(t);break;case"multiple":("object"!=typeof e||void 0==e.length)&&(e=[e]),s.dates=[],s.datesText=[];var n=this;$.map(e,function(e){$.datepicker._setDate_original(t,e,i),s.dates.push(n._getDate(t)),s.datesText.push(n._formatDate(t))}),s.setClassActive(t)}};var _datepickerExtension=function(){this.range=!1,this.range_multiple_max=0,this.step=0,this.dates=[],this.datesText=[],this.startDate=null,this.endDate=null,this.startDateText="",this.endDateText="",this.onSelect=function(t,e){switch(this.range){case"period":return this.onSelectPeriod(t,e);case"multiple":return this.onSelectMultiple(t,e)}},this.onSelectPeriod=function(t,e){this.step++,this.step%=2,this.step?(this.startDate=this.getSelectedDate(e),this.endDate=this.startDate,this.startDateText=t,this.endDateText=this.startDateText):(this.endDate=this.getSelectedDate(e),this.endDateText=t,this.startDate.getTime()>this.endDate.getTime()&&(this.endDate=this.startDate,this.startDate=this.getSelectedDate(e),this.endDateText=this.startDateText,this.startDateText=t))},this.onSelectMultiple=function(t,e){var i=this.getSelectedDate(e),a=-1;$.map(this.dates,function(t,e){t.getTime()==i.getTime()&&(a=e)});var s=$.inArray(t,this.datesText);-1!=a?this.dates.splice(a,1):this.dates.push(i),-1!=s?this.datesText.splice(s,1):this.datesText.push(t),this.range_multiple_max&&this.dates.length>this.range_multiple_max&&(this.dates.splice(0,1),this.datesText.splice(0,1))},this.fillDay=function(t,e){var i=e[1];switch(1==t.getDate()&&(i+=" first-of-month"),t.getDate()==new Date(t.getFullYear(),t.getMonth()+1,0).getDate()&&(i+=" last-of-month"),e[1]=i.trim(),this.range){case"period":return this.fillDayPeriod(t,e);case"multiple":return this.fillDayMultiple(t,e)}},this.fillDayPeriod=function(t,e){if(!this.startDate||!this.endDate)return e;var i=e[1];return t>=this.startDate&&t<=this.endDate&&(i+=" selected"),t.getTime()==this.startDate.getTime()&&(i+=" selected-start"),t.getTime()==this.endDate.getTime()&&(i+=" selected-end"),e[1]=i.trim(),e},this.fillDayMultiple=function(t,e){var i=e[1],a=!1;return $.map(this.dates,function(e){e.getTime()==t.getTime()&&(a=!0)}),a&&(i+=" selected selected-start selected-end"),e[1]=i.trim(),e},this.getSelectedDate=function(t){return new Date(t.selectedYear,t.selectedMonth,t.selectedDay)},this.setClassActive=function(t){var e=this;setTimeout(function(){$("td.selected > *",t.dpDiv).addClass("ui-state-active"),"multiple"==e.range&&$("td:not(.selected)",t.dpDiv).removeClass("ui-datepicker-current-day").children().removeClass("ui-state-active")})}};

Подскажите, а как передать параметры дат, чтобы были выбраны при загрузке плагина?

Можно установить нужные даты с помощью метода setDate:

var $datePicker = $('#datepicker');
$datePicker.datepicker('setDate', ['-1w +1d', '+0d']); // период - последняя неделя

при multiple по умолчанию выбрана сегодняшняя дата, как от этого избавится? чтобы при мервом нажатии в массив передавалась только 1 дата
разобрался
при инициализации

$('#_datepicker').datepicker('widget').data('datepickerExtensionRange', '');