Get next date from weekday in JavaScript

Question

How can one return the next date of a given weekday (it could be either a number 0-6 or names Sunday-Saturday).

Example, if today, on Friday

Answer 1

And if you do not want do pass numbers but weekday-names (sunday - saturday) to find a future date of a certain weekday, then this helps you as well:

function getDateOfWeekday(refday){
    var days = {
        monday: 1,
        tuesday: 2,
        wednesday: 3,
        thursday: 4,
        friday: 5,
        saturday: 6,
        sunday: 0
    };
    if(!days.hasOwnProperty(refday))throw new Error(refday+" is not listed in "+JSON.stringify(days));
    var currDate = new Date();
    var currTimestamp = currDate.getTime();
    var triggerDay = days[refday];
    var dayMillDiff=0;
    var dayInMill = 1000*60*60*24;
    // add a day to dayMillDiff as long as the desired refday (sunday for instance) is not reached
    while(currDate.getDay()!=triggerDay){
        dayMillDiff += dayInMill;
        currDate = new Date(currDate.getTime()+dayInMill);
    }
    return new Date(currTimestamp + dayMillDiff);
}

var sunday = getDateOfWeekday("sunday");
document.write("Next Sunday is at: "+sunday.toLocaleString()+"
");

var thursday = getDateOfWeekday("thursday");
thursday.setHours(0,0,0,0); // set hours/minutes/seconds and millseconds to zero
document.write("Next Thursday is at: "+thursday.toLocaleString()+" on midnight
");

var tuesday = getDateOfWeekday("tuesday");
document.write("Next Tuesday is at: "+tuesday.toLocaleString()+"
");