Combined Comparison / "Spaceship" Operator (<=>) in Javascript?

Question

Ruby has something called a Combined Comparison or "Spaceship" Operator, it looks like this: <=>

It does the following:

a <=> b :=
    if a < b then return -1
    if a = b then return  0
    if a > b then return  1

Credit

Is there a similar Operator in Javascript? If not, how can I end up with the same result?

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@madox2 suggested using Math.sign(a - b), which works for number, but not arrays (to compare arrays you need to use array.length).

It also does not work in Internet Explorer, Safari or all Mobile Browsers (see MDN)

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@duques_l found a function here. It works very well, you can test it on JSFiddle

The only problem is if the strings are not comparable the function returns -1 instead of nil

Update: @duques_l changed the function a bit and now it works fine (I think so anyway, here is the JSFiddle):

function spaceship(val1, val2) {
    if ((val1 === null || val2 === null) || (typeof val1 != typeof val2)) {
        return null;
    }
    if (typeof val1 === 'string') {
        return (val1).localeCompare(val2);
    }
    else {
        if (val1 > val2) { return 1 }
        else if (val1 < val2) { return -1 }
        return 0;
    }
}

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Premonition

doesn't exist, but sabrelabs.com/post/48201437312/javascript-spaceship-operator – Acrimony

@duques_l Interesting link. That function does seem to do just that! – Premonition

Answer 1

As far as I know there is no such operator in JavaScript but you can use Math.sign() function:

Math.sign(a - b);

NOTE: As was mentioned in comments, Math.sign() is not currently supported by all browsers. Check for compatibility (MDN).

Finned

This works for numbers, but not arrays (well, you have to use array.length). Clever solution though! – Premonition

if there is one, not in ie. – Judicator

@NinaScholz If there is one what? – Premonition

@Druzion, the Internet Explorer does not have Math.sign(). – Judicator

@NinaScholz Ah yes, it is also not supported in Safari and all Mobile Browsers, according to MDN – Premonition

As of today and according to CanIUse.com : Math.sign is supported by almost 95% browsers. If your target clients is that guys who update their browsers, you can assume it's now safe to use it. – Keelby

For those desperate to support Legacy Browsers: if(!Math.sign) Math.sign=function(value) {return value?(value<0?-1:1):0}; will do for a polyfill. – Craftsman

Answer 2

from: http://sabrelabs.com/post/48201437312/javascript-spaceship-operator

improved version:

function spaceship(val1, val2) {
  if ((val1 === null || val2 === null) || (typeof val1 != typeof val2)) {
    return null;
  }
  if (typeof val1 === 'string') {
    return (val1).localeCompare(val2);
  } else {
    if (val1 > val2) {
      return 1;
    } else if (val1 < val2) {
      return -1;
    }
    return 0;
  }
}

Jeanelle

No, if the data types are different, it returns 0. Check the new JSFiddle – Premonition

it's fixed, can you check ? – Acrimony

nil doesn't exist in javascript, it's null – Acrimony

I think that function is a bit over-engineered lol – Misology

Answer 3

Here is a one-liner for current js ES2020?:

const spaceship = (a, b) => (a ?? 0).toString().localeCompare((b ?? 0).toString());

Returns string comparison for everything.

Decastere

As this uses string comparison for numbers, it can give invalid results for inputs with a different quantity of digits, e.g. spaceship(100, 2) will result in -1 (as it's effectively sorting alphabetically and the first "letter", 1 is "less" than 2) – Knuth

As this uses string comparison for everything, objects and arrays will not sort... as their string representation will be '[object Object]' and that is equal to itself. 0 is neither -1 or 1. – Decastere