Am I witnessing operator-overloading in JavaScript?

Question

I thought that there was no such thing as operator-overloading in JavaScript.

Then I noticed that when using this BigNumber class, I can actually do subtraction:

let a = new BigNumber("5432");
let b = new BigNumber(1234);
let c = a - b;
console.log(c); // 4198

How is it possible, or what am I missing here?

I don't know what makes you think this is operator-overloading, BigNumber returns a number, the docs say that the quotes are because they called a preceding .toString(). You're subtracting 2 Numbers here — Sterling Archer
– Sterling Archer, Commented Jan 30, 2018 at 19:50
I checked it via console.log(typeof a) and got Object, not Number. — goodvibration
– goodvibration, Commented Jan 30, 2018 at 19:53
Possible duplicate of Overloading Arithmetic Operators in JavaScript? — Ele
– Ele, Commented Jan 30, 2018 at 19:54

Daniel A. White · Accepted Answer · 2018-01-30 19:53:21Z

3

JavaScript doesn't have operator overloading.

BigNumber.prototype.valueOf is provided which returns a value. Read up on valueOf.

From MDN:

function MyNumberType(n) {
    this.number = n;
}

MyNumberType.prototype.valueOf = function() {
    return this.number;
};

var myObj = new MyNumberType(4);
myObj + 3; // 7

edited Jan 30, 2018 at 19:53

answered Jan 30, 2018 at 19:50

Daniel A. White

192k49 gold badges389 silver badges473 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

goodvibration Over a year ago

I don't understand from your answer, how the expression a - b is executed / evaluated.

goodvibration Over a year ago

Oh, is it a.valueOf() - b.valueOf()?

goodvibration Over a year ago

So then I'm at risk losing precision in that case, right?

goodvibration Over a year ago

OK, I'll rephrase that: Speculating from the name "BigNumber", I'm at risk losing precision in your subjective opinion?

goodvibration Over a year ago

@General_Twyckenham: I used "-" by mistake, and my code was running flawless. Then I realized that I should have used "minus", so was wondering how come it worked without it.

|

Collectives™ on Stack Overflow

Am I witnessing operator-overloading in JavaScript?

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related