Date Modification - Pure Javascript

by Mike Gleeson

JavaScript

var MS_PER_MINUTE = 60000;
var MS_PER_HOUR = MS_PER_MINUTE*60;
var MS_PER_DAY = MS_PER_HOUR*24;
var MS_PER_WEEK = MS_PER_DAY*7;



function alertDate(){
    var NUM_WEEKS = prompt("Please enter a number of weeks in the past", "10");
    var _DATE_ = new Date()-MS_PER_WEEK*NUM_WEEKS;

    if (NUM_WEEKS != null && !isNaN(NUM_WEEKS)) {
        alert(new Date(_DATE_));
    }
}

alertDate();