Guide on verifying if a variable is a tuple in TypeScript

Question

Guide on verifying if a variable is a tuple in TypeScript

I am attempting to determine if a variable passed to a function, which can either be an array of numbers or an array of tuples, is the array of tuples.

function (times: Array<number> | Array<[number, number]>) {
    if (Array.isArray(times[0]) && times[0].length === 2 && typeof times[0][0] === 'number' && typeof times[0][1] === 'number') {
        console.log("It's the tuple one!");
    }
}

The code above is not functioning as expected. I have also attempted using if (times[0] instanceof tuple)), but that did not work either. Is there a way to achieve this?

Thank you!

typescript

Answer 1

Answer №1

As per the Tuple section of Basic Types documentation:

Tuple types enable you to define an array where a specific number of elements have known types, but those types do not necessarily have to be identical.

This implies that tuples essentially function like arrays.
Furthermore, since typescript translates to javascript and javascript does not support tuples, verifying the type during runtime requires cross-referencing with javascript types rather than typescript ones which are non-existent during runtime.

To address your query:

function fn(times: Array<number> | Array<[number, number]>) {
    if (times[0] instanceof Array) {
        console.log("This is the tuple scenario!");
    }
}

Answer 2

As per the Tuple section of Basic Types documentation:

Tuple types enable you to define an array where a specific number of elements have known types, but those types do not necessarily have to be identical.

This implies that tuples essentially function like arrays.
Furthermore, since typescript translates to javascript and javascript does not support tuples, verifying the type during runtime requires cross-referencing with javascript types rather than typescript ones which are non-existent during runtime.

To address your query:

function fn(times: Array<number> | Array<[number, number]>) {
    if (times[0] instanceof Array) {
        console.log("This is the tuple scenario!");
    }
}

Guide on verifying if a variable is a tuple in TypeScript

Answer №1

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