Determining Date Equality in Javascript

Question

I need to find out if two dates the user selects are the same in Javascript. The dates are passed to this function in a String ("xx/xx/xxxx").That is all the granularity I need.

Here is my code:

        var valid = true;
    var d1 = new Date($('#datein').val());
    var d2 = new Date($('#dateout').val());
    alert(d1+"\n"+d2);
    if(d1 > d2) {
        alert("Your check out date must be after your check in date.");
        valid = false;
    } else if(d1 == d2) {
        alert("You cannot check out on the same day you check in.");
        valid = false;
    }

The javascript alert after converting the dates to objects looks like this:

Tue Jan 25 2011 00:00:00 GMT-0800 (Pacific Standard Time)

Tue Jan 25 2011 00:00:00 GMT-0800 (Pacific Standard Time)

The test to determine if date 1 is greater than date 2 works. But using the == or === operators do not change valid to false.

Hydrogenous

Have you checked this post out: #338963. Does it help? – Dannielledannon

Tempted to flag this as a duplicate but I think this is a fringe case of the same issue, so I'm not. – Vevine

This is not a duplicate. The post mentionned (and the accepted answer) are about determining if a date is before or after another, not about equality. – Ranket

Answer 1

Use the getTime() method. It will check the numeric value of the date and it will work for both the greater than/less than checks as well as the equals checks.

EDIT:

if (d1.getTime() === d2.getTime())

Crossquestion

And the stackoverflow question I posted above shows an example. The questions were identical. – Dannielledannon

A simpler way: if( +d1 == +d2 ) – Wilton

Answer 2

If you don't want to call getTime() just try this:

(a >= b && a <= b)

Witkin

WTF? Why does that work but the equality operator does not? Where is the sense in that? – Michal

The equality operator checks for reference equality. This means it only returns true if the two variables refer the the same object. If you create two Date objects (var a = new Date(); var b = new Date();), they will never be equal. – Daryldaryle

Is this not a JS bug or is it a limitation of the equality operator and overloading ability? – Blessed

This is what equality does for objects, it checks references. – Witkin

@Witkin except for string, that are compared by value also, var a ="str1"; var b = "str"+"1"; a == b // true – Unsteel

wierd. You would have thought this would have actually been a place where a seperation between == and === would make sense... Oh wait its javascript. We dont do sense here! – Reply

@Towa, That works because the >= and <= operators only work on numbers, so they try to convert their operands to numbers. And to convert an object (such as a Date) to a number, JavaScript calls the valueOf() function to get a numeric representation. valueOf() returns the same thing as getTime(): developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… – Acidic

Answer 3

var d1 = new Date($('#datein').val());
var d2 = new Date($('#dateout').val());

use two simple ways to check equality

1. if( d1.toString() === d2.toString())
2. if( +d1 === +d2)

Orlan

Answer 4

Instead of comparing the dates directly, you can check that their difference is zero.

if (d1 - d2 === 0)

Jelene

Answer 5

var date = "Wed Oct 07 2015 19:48:08 GMT+0200 (Central European Daylight Time)";

var dateOne = new Date(date);
var dateTwo = new Date();

var isEqual = dateOne.getDate() === dateTwo.getDate()

this will give you the dates equality

Chronometry

The community encourages adding explanations alongisde code, rather than purely code-based answers (see here). – Glynn

This is wrong. The 7th April is not the same as the 7th March. – Creon