Adding hours to JavaScript Date object?

Question

It amazes me that JavaScript\'s Date object does not implement an add function of any kind.

I simply want a function that can do this:

var now = Date         


        

Answer 1

Check if its not already defined, otherwise defines it on the Date prototype:

if (!Date.prototype.addHours) {
    Date.prototype.addHours = function(h) {
        this.setHours(this.getHours() + h);
        return this;
    };
}

Answer 2

For a simple add/subtract hour/minute function in javascript, try this:

function getTime (addHour, addMin){
    addHour = (addHour?addHour:0);
    addMin = (addMin?addMin:0);
    var time = new Date(new Date().getTime());
    var AM = true;
    var ndble = 0;
    var hours, newHour, overHour, newMin, overMin;
    //change form 24 to 12 hour clock
    if(time.getHours() >= 13){
        hours = time.getHours() - 12;
        AM = (hours>=12?true:false);
    }else{
        hours = time.getHours();
        AM = (hours>=12?false:true);
    }
    //get the current minutes
    var minutes = time.getMinutes();
    // set minute
    if((minutes+addMin) >= 60 || (minutes+addMin)<0){
        overMin = (minutes+addMin)%60;
        overHour = Math.floor((minutes+addMin-Math.abs(overMin))/60);
        if(overMin<0){
            overMin = overMin+60;
            overHour = overHour-Math.floor(overMin/60);
        }
        newMin = String((overMin<10?'0':'')+overMin);
        addHour = addHour+overHour;
    }else{
        newMin = minutes+addMin;
        newMin = String((newMin<10?'0':'')+newMin);
    }
    //set hour
    if(( hours+addHour>=13 )||( hours+addHour<=0 )){
        overHour = (hours+addHour)%12;
        ndble = Math.floor(Math.abs((hours+addHour)/12));
        if(overHour<=0){
            newHour = overHour+12;
            if(overHour == 0){
                ndble++;
            }
        }else{
            if(overHour ==0 ){
                newHour = 12;
                ndble++;
            }else{
                ndble++;
                newHour = overHour;
            }
        }
        newHour = (newHour<10?'0':'')+String(newHour);
        AM = ((ndble+1)%2===0)?AM:!AM;
    }else{
        AM = (hours+addHour==12?!AM:AM);
        newHour = String((Number(hours)+addHour<10?'0':'')+(hours+addHour));
    }
    var am = (AM)?'AM':'PM';
    return new Array(newHour, newMin, am);
};

This can be used without parameters to get the current time

getTime();

or with parameters to get the time with the added minutes/hours

getTime(1,30); // adds 1.5 hours to current time
getTime(2);    // adds 2 hours to current time
getTime(0,120); // same as above

even negative time works

getTime(-1, -30); // subtracts 1.5 hours from current time

this function returns an array of

array([Hour], [Minute], [Meridian])

Answer 3

I also think the original object should not be modified. So to save future manpower here's a combined solution based on Jason Harwig's and Tahir Hasan answers:

Date.prototype.addHours= function(h){
    var copiedDate = new Date();
    copiedDate.setTime(this.getTime() + (h*60*60*1000)); 
    return copiedDate;
}

Answer 4

If someone is still looking at this issue, the easiest way to do is

var d = new Date();
d.setHours(15);