Subtracting days/months/years from a Date object

Question

var inputDate     = \'20/4/2010\'.split(\'/\');
var dateFormatted = new Date(parseInt(inputDate[2]), parseInt(inputDate[1]), parseInt(inputDate[0]));

var expiryDate         


        

Answer 1

Easy way to see if a date inputed is a valid date:

var d = Date.parse('4/20/2010');
if (isNaN(d.valueOf())) {
 alert ("bad date value"); 
}

Then, here is a dateAdd function that I use regularly. Extends the Date object, so it's easy to use:

Date.prototype.dateAdd = function(size,value) {
    value = parseInt(value);
    var incr = 0;
    switch (size) {
        case 'day':
            incr = value * 24;
            this.dateAdd('hour',incr);
            break;
        case 'hour':
            incr = value * 60;
            this.dateAdd('minute',incr);
            break;
        case 'week':
            incr = value * 7;
            this.dateAdd('day',incr);
            break;
        case 'minute':
            incr = value * 60;
            this.dateAdd('second',incr);
            break;
        case 'second':
            incr = value * 1000;
            this.dateAdd('millisecond',incr);
            break;
        case 'month':
            value = value + this.getUTCMonth();
            if (value/12>0) {
                this.dateAdd('year',value/12);
                value = value % 12;
            }
            this.setUTCMonth(value);
            break;
        case 'millisecond':
            this.setTime(this.getTime() + value);
            break;
        case 'year':
            this.setFullYear(this.getUTCFullYear()+value);
            break;
        default:
            throw new Error('Invalid date increment passed');
            break;
    }
}

Then just use:

 var d = new Date();
 d.dateAdd('day', -1).dateAdd('year', 3);

T'da