Typescript: Combined Comparison (Spaceship) Operator

[ArchSonix]

Search Terms

• Three-way comparison
• spaceship operator
• <=>

Suggestion

Add a new operator (expr) <=> (expr), it returns 0 if both operands are equal, 1 if the left is greater, and -1 if the right is greater. It uses exactly the same comparison rules as used by the existing comparison operators: <, <=, ==, >= and >

References

• Wikipedia: https://en.wikipedia.org/wiki/Three-way_comparison#High-level_languages
• PHP implementation: https://wiki.php.net/rfc/combined-comparison-operator

Use Cases

_What do you want to use this for?_ / _What shortcomings exist with current approaches?_
This removes much boilerplate code when writing sorting functions, although it could be useful in other instances as well.

Examples

Basic use case with current syntax:

data = data.sort((a, b) => {
    if (a.value > b.value) {
        return 1;
    } else if (a.value < b.value) {
        return -1;
    } else {
        return 0;
    }
});

new syntax:

data = data.sort((a, b) => {
    return a.value <=> b.value;
});

Checklist

My suggestion meets these guidelines:

• [x] This wouldn't be a breaking change in existing TypeScript / JavaScript code
• [x] This wouldn't change the runtime behavior of existing JavaScript code
• [x] This could be implemented without emitting different JS based on the types of the expressions
• [ ] This isn't a runtime feature (e.g. new expression-level syntax)

[Kingwl]

i think - operator is what you said 😂

data.sort((a, b) => a - b);

[kpdonn]

In addition to that:

• [x] This isn't a runtime feature (e.g. new expression-level syntax)

Yes it is.

[ArchSonix]

@Kingwl @kpdonn Oh man, I didn't think of that, thanks for the pointer. ^^

[stewsters]

The - operator does not work on strings, though, correct? If you are finding this and need to use it on strings, take a look at String.localeCompare().

[olvenmage]

Doesnt work on strings or arrays, also, the funciton does accept numbers lower than -1 and higher than 1 but this is not intended. So it's always better, to ensure full support in the future, to just use -1, 0 and 1.

[dpinol]

Several languages have it. It's very useful to have a standard way to compare instances
https://en.wikipedia.org/w/index.php?title=Three-way_comparison&section=2#High-level_languages