2ality – JavaScript and more - Latest Comments in Fake operator overloading in JavaScript

Re: Fake operator overloading in JavaScript

Pavel Melnikov — Sat, 28 Jul 2018 08:48:07 -0000

Lol, I made package that overload bracket operator [] https://github.com/munrocke...

Re: Fake operator overloading in JavaScript

Sasha Firsov — Tue, 26 Jun 2018 17:17:41 -0000

That operators overload technique is brilliant! Even 6 years later, with new JS standards around it has a perfect sense. Love it!

Re: Fake operator overloading in JavaScript

Andrew Keats — Sat, 20 Jan 2018 22:21:31 -0000

Not sure how I feel about this, amazing 'hack' but I'm certainly impressed!

Re: Fake operator overloading in JavaScript

Misha Sulikashvili — Sat, 02 Dec 2017 11:10:14 -0000

Thanks Axel for this great article.
You made my life easy <3

Re: Fake operator overloading in JavaScript

Kevin Zeidler — Sat, 02 Jul 2016 21:19:22 -0000

Thanks, Axel. Your site is quickly becoming my 'go-to' reference for all my Javascript questions. Terrific explanations of how to implement all my favorite language features.

Re: Fake operator overloading in JavaScript

Agradip — Fri, 01 May 2015 21:45:11 -0000

Axel Raushmayer, is it possible run this on browser enviroment. git repo example works on server env .https://github.com/rauschma/op_over...

Re: Fake operator overloading in JavaScript

Filip Zawada — Mon, 28 Jul 2014 07:42:42 -0000

This seems similar to the concept of operator overloading I used in Fingers.js (initially done for AS3, later ported to JS). It overloads valueOf for adding .NET style event listeners:

function hi() { console.log("hi") } function twoality() { console.log("2ality") } function bye() { console.log("bye") } on(yourButton).click += hi + twoality; on(yourButton).click -= hi - bye;

I've got an article explaining how it works, maybe helpful for some readers.

Cheers!
Filip

Re: Fake operator overloading in JavaScript

mor — Tue, 17 Jun 2014 12:03:12 -0000

Some operators even convert their right operands first:

> func("LEFT") > func("RIGHT")
func_LEFT
func_RIGHT
valueOf_RIGHT
valueOf_LEFT

But when i run it in recent ff\chrome console look like in first case.Why?

Re: Fake operator overloading in JavaScript

Axel Rauschmayer — Sun, 29 Jan 2012 07:44:42 -0000

There it is short-circuiting plus associativity. It is very unusual for an operator not to first evaluate all of its operands. || and && are special here. As you mention, || only evaluates its second operand if its first operand is false.

Re: Fake operator overloading in JavaScript

Axel Rauschmayer — Sun, 29 Jan 2012 07:19:16 -0000

Fixed the typo, thanks. Can you format your comment with PRE tags? Then it is easier to read.

Re: Fake operator overloading in JavaScript

dotnetCarpenter — Mon, 09 Jan 2012 22:38:24 -0000

Typo x + x
y - x <- y should be x (produces 0)
x * x
x / xWhile you make clever use of the different signatures the above produce wouldn't italso be possible to achieve a similar effect by using enumeration values?E.I. Object.defineProperty(Point.prototype, "_", { set: function (value) { var ops = Point.operands; var operator; switch (value) { case valEnum.do : console.log('do -> 1'); operator = this.setSubtract; break; case valEnum.another : console.log('another -> 2'); operator = this.setAdd; break; case valEnum.thing : console.log('thing -> 4'); break; case (valEnum.another+valEnum.thing) console.log('another thing -> 6'); operator = this.setMultiply; break; default: throw new Error("Unsupported operation (code "+value+")"); } Point.operands = []; // reset return operator.apply(this, ops); } });var valEnum = { do: 1, another: 2, thing: 4}Point.prototype.valueOf = function () { Point.operands.push(this); return valEnum.another;}On seconds thought.. no not really.

Re: Fake operator overloading in JavaScript

Juho Vepsäläinen — Fri, 23 Dec 2011 11:59:17 -0000

It's possible to use JSShaper and little AST trickery allow proper operator overloading. See http://nixtu.blogspot.com/2... . I believe this is close to what Dart uses these days.

Re: Fake operator overloading in JavaScript

Romain Guerin — Wed, 21 Dec 2011 15:46:04 -0000

Nice :)

It is the same underlying effect that don't call the method in this example (it stops on the first truthy value) ?
myVar || true || myFunc()

Re: Fake operator overloading in JavaScript

Axel Rauschmayer — Mon, 19 Dec 2011 18:18:28 -0000

Yes, interesting. It is associativity at work:
a << b << c === (a << b) << c

Re: Fake operator overloading in JavaScript

PaulGrenier — Mon, 19 Dec 2011 14:17:39 -0000

Something I found interesting: When you chain further operators (like func("LEFT") >> func("MIDDLE") >> func("RIGHT");) the additional func calls are not made until the first two have concluded their underlying operator business (bitshifting, modulous, etc.). So, in the above example you get:
func_LEFTfunc_MIDDLEvalueOf_LEFTtoString_LEFTvalueOf_MIDDLEtoString_MIDDLEfunc_RIGHTvalueOf_RIGHTtoString_RIGHT

Maybe that has some value... just gotta figure out what that is :P

Re: Fake operator overloading in JavaScript

Axel Rauschmayer — Sun, 18 Dec 2011 09:36:13 -0000

See the new section “Detecting the operator”.

Re: Fake operator overloading in JavaScript

Dan — Sat, 17 Dec 2011 19:12:28 -0000

I met with similar approach when I was trying to find out how operators work in Paper.js.
Is there any way how to find out which operator called the valueOf function?

Imagine simple Point object and attempt to perform basic math operation. E.g. p1 + p2 = p3 and p3 has sum x and y coordinates, with this approach it would be possible to make it work for one operator but not for all of them (+; -; /; *; ...).

I would not like to wrap whole piece of code into some function or compile it as paper.js does but it's the only solution is not it?