How to compare DateTimes and ClockTimes?

[shaulbehr]

It appears the comparison operators haven't been implemented for DateTime, ClockTime etc. Thus:

let lt = dateA < dateB; // evaluates to false
let gt = dateA > dateB; // evaluates to false
let eq = dateA == dateB; // evaluates to false

How should I compare these DateTime values?

[electricessence]

I will add IEquatable interface to these. Should be ready soon.

[electricessence]

Some of these classes already have IEquatable.

[electricessence]

BTW, in JS you can't compare two Date objects either:

var d1 = new Date(2012,12,11);
var d2 = new Date(2012,12,11);
var e = d1==d2; /* false */
var ev = d1.getTime()==d2.getTime(); /* true */

[electricessence]

Please review. Dates have always been a pain in JS because of time zones. Take a look at this code and see what you think. The equals is simple and stupid but maybe the equivalent method could be more useful.

    /**
     * Compares a JS Date with the current instance.  Does not evaluate the kind.
     * @param other
     * @returns {boolean}
     */
    equals(other:Date):boolean

    /**
     * Compares another IDateTime object and returns true if they or their value are equal.
     * @param other The other IDateTime object.
     * @param strict When strict is true, the 'kind' also must match.
     * @returns {boolean}
     */
    equals(other:IDateTime, strict?:boolean):boolean

    equals(other:IDateTime | Date, strict:boolean = false):boolean
    {
        if(!other) return false;
        if(other==this) return true;

        if(other instanceof Date)
        {
            let v = this._value;
            return other==v || other.getTime()==v.getTime();
        }

        if(other instanceof DateTime)
        {
            if(strict)
            {
                let ok = other._kind;
                if(!ok && this._kind || ok!=this._kind) return false;
            }

            return this.equals(other._value);
        }
        else if(strict)
            return false;

        return this.equals(other.toJsDate());

    }

    equivalent(other:IDateTime | Date):boolean
    {
        if(!other) return false;
        if(other==this) return true;

        if(other instanceof Date)
        {
            let v = this._value;
            // TODO: What is the best way to handle this when kinds match or don't?
            return v.toUTCString()==other.toUTCString();
        }

        if(other instanceof DateTime)
        {
            if(this.equals(other, true)) return true;
        }

        return this.equivalent(other.toJsDate());
    }

[electricessence]

Here's the actual change: https://github.com/electricessence/TypeScript.NET/commit/c6072d83fb7b95eeff8811539673da2ec78d3534#diff-f5c5c14b1129c431e6a0a61f9634559e It has been published to NPM and can be used now. Would still appreciate a review.

[shaulbehr]

Thanks for this! Can I also request implementations of <, <=, > and >=, please? :-)

[electricessence]

Ok so an IComparable interface... Will do. Again would appreciate some review and tell me if you think the way I'm implementing makes sense to developers. The equals method is a bit strict here.

[electricessence]

But there's no operator extensions in JS so I can't just add them like in C#.

[shaulbehr]

But there's no operator extensions in JS so I can't just add them like in C#.

Rats. That's a bit of a bummer. So even for equivalence comparison, I have to use .equals() or .equivalent(), not == or ===? (As you can see, I'm kinda new to TypeScript.)

[electricessence]

Well... Again already in existence is... https://www.w3schools.com/jsref/jsref_getTime.asp You get the milliseconds (.getTime()) from any Date and you can compare them. So as a fallback all DateTime objects in TypeScript .NET have .toJsDate() which gives you a copy of the internal date object. With the milliseconds you can easily >=, <=, <, > or whatever.

For sorting purposes, DateTime objects should have IComparable otherwise you'd have to write your own comparer.

[electricessence]

Here's the tests I added for that.

    it("should compare correctly",()=>{
        const x = new DateTime(d1), y = new DateTime(d2), z = new DateTime(d2);
        assert.ok(x.compareTo(y)<0);
        assert.ok(y.compareTo(x)>0);
        assert.ok(y.compareTo(z)==0);
    });

[electricessence]

New patched version is now published. Note that all TimeQuantity classes already have IComparable implemented.

[electricessence]

@shaulbehr If you want to support my efforts, take my Udemy course: :) https://www.udemy.com/stepping-up-to-typescript-fundamentals/ Could use another positive review or two.

[shaulbehr]

New patched version is now published. Note that all TimeQuantity classes already have IComparable implemented.

Terrific! Thanks for your super-speedy responses - really appreciated. What version contains these patches?

[electricessence]

@shaulbehr latest on NPM

[shaulbehr]

Hm, comparing two ClockTimes is causing an exception: My code:

if (now.compareTo(todayHours.localStartTime) < 0) { ... }

Exception:

TypeError: Can't add property _total, object is not extensible at n.get [as total] (TimeQuantity.js:formatted:1) at n.t.compareTo (TimeQuantity.js:formatted:1) at SchoolHoursManagementService.setOutsideSchoolHours (school-hours-management.service.ts:112) at school-hours-management.service.ts:55 at ZoneDelegate.invoke (TimeQuantity.js:formatted:1) at Object.onInvoke (TimeQuantity.js:formatted:1) at ZoneDelegate.invoke (TimeQuantity.js:formatted:1) at Zone.run (TimeQuantity.js:formatted:1) at TimeQuantity.js:formatted:1 at ZoneDelegate.invokeTask (TimeQuantity.js:formatted:1) at Object.onInvokeTask (TimeQuantity.js:formatted:1) at ZoneDelegate.invokeTask (TimeQuantity.js:formatted:1) at Zone.runTask (TimeQuantity.js:formatted:1) at drainMicroTaskQueue (TimeQuantity.js:formatted:1) at IDBRequest.ZoneTask.invoke (TimeQuantity.js:formatted:1)

[electricessence]

Hey sorry for the delay on this. I'll get to it asap.

[electricessence]

Ok. This is fixed and published as 4.8.0. I added a couple more unit tests to make sure that comparisons are covered in Time classes other than DateTime.