JavaScriptMovieCalendar/date.js at master · ikegee/JavaScriptMovieCalendar · GitHub

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/**
 * @file date.js
 * @description Calendar helpers on the native Date prototype (side-effect module).
 * Used by date-display.js and calendar.js for week/month navigation and YYYY_MM_DD keys.
 * @author Thomas Lane
 * @version $Revision: 453 $
 * $Date: 2012-01-17 15:38:39 -0800 (Tue, 17 Jan 2012) $
 * @modified G.E. Eidsness
 * @version $Revisions: 001 $
 * $Date: 2023-11-17 00:46:39 -0700 (Fri, 17 Nov 2023) $
 * @version $Rewrite: 001 $
 * $Date: 2026-07-28 11:36:29 -0700 (Tue, 28 July 2026) $
 */

// Separator for delimited date strings (matches jsonShows/ file naming)
Date.DELIM="_";

// Week bounds (Sunday-start calendar)
Date.WEEKSTART=0;
Date.WEEKEND=6;

/**
 * @returns {string} Day of week as an English word
 */
Date.prototype.getDayWord=function(){
returnthis.toLocaleDateString("en-US",{weekday: "long"});
};

/**
 * @returns {string} Month of year as an English word
 */
Date.prototype.getMonthWord=function(){
// Use local month (not UTC) so names match getMonth()/getDelimDate()
returnthis.toLocaleDateString("en-US",{month: "long"});
};

/**
 * @returns {Date} First day of this date's month
 */
Date.prototype.getMonthStart=function(){
returnnewDate(this.getFullYear(),this.getMonth(),1);
};

/**
 * @returns {Date} Last day of this date's month
 */
Date.prototype.getMonthEnd=function(){
returnnewDate(this.getFullYear(),this.getMonth()+1,0);
};

/**
 * @returns {Date} First day of this date's week (Sunday)
 */
Date.prototype.getWeekStart=function(){
returnnewDate(
this.getFullYear(),
this.getMonth(),
this.getDate()-(this.getDay()-Date.WEEKSTART)
);
};

/**
 * @returns {Date} Last day of this date's week (Saturday)
 */
Date.prototype.getWeekEnd=function(){
returnnewDate(
this.getFullYear(),
this.getMonth(),
this.getDate()+(Date.WEEKEND-this.getDay())
);
};

/**
 * Mutates this date forward by one day.
 */
Date.prototype.incrementByDay=function(){
this.setDate(this.getDate()+1);
};

/**
 * Mutates this date backward by one day.
 */
Date.prototype.decrementByDay=function(){
this.setDate(this.getDate()-1);
};

/**
 * Mutates this date forward by seven days.
 */
Date.prototype.incrementByWeek=function(){
this.setDate(this.getDate()+7);
};

/**
 * Mutates this date backward by seven days.
 */
Date.prototype.decrementByWeek=function(){
this.setDate(this.getDate()-7);
};

/**
 * Mutates this date forward by one month, clamping the day if needed
 * (e.g. Jan 31 → Feb 28/29 instead of skipping to March).
 */
Date.prototype.incrementByMonth=function(){
constfirstNextMonth=newDate(this.getFullYear(),this.getMonth()+1,1);
constsameDayNextMonth=newDate(
this.getFullYear(),
this.getMonth()+1,
this.getDate()
);

if(sameDayNextMonth.getMonth()!==firstNextMonth.getMonth()){
this.setDate(firstNextMonth.getMonthEnd().getDate());
this.setMonth(firstNextMonth.getMonth());
}else{
this.setMonth(this.getMonth()+1);
}
};

/**
 * Mutates this date backward by one month, clamping the day if needed
 * (e.g. Mar 31 → Feb 28/29 instead of landing on Mar 2/3).
 */
Date.prototype.decrementByMonth=function(){
constlastPrevMonth=this.getMonthStart();
lastPrevMonth.decrementByDay();

constsameDayPrevMonth=newDate(
this.getFullYear(),
this.getMonth()-1,
this.getDate()
);

if(sameDayPrevMonth.getTime()>lastPrevMonth.getTime()){
this.setDate(lastPrevMonth.getDate());
this.setMonth(lastPrevMonth.getMonth());
}else{
this.setMonth(this.getMonth()-1);
}
};

/**
 * @returns {string} Date as YYYY_MM_DD (zero-padded month and day)
 */
Date.prototype.getDelimDate=function(){
constyear=this.getFullYear();
constmonth=String(this.getMonth()+1).padStart(2,"0");
constday=String(this.getDate()).padStart(2,"0");
returnyear+Date.DELIM+month+Date.DELIM+day;
};