typescript set type depending on value

Question

I have a function that takes in an optional variant and a value. If the variant is multi the user needs to use a tuple, otherwise a number. Is there any way to type this dynamically? Conceptually it should work like this:

interface SomeInterface{
  variant?: 'single' | 'multi'
  // pseudocode
  value: variant === 'multi' ? [number,number] : number
}

cubefox · Accepted Answer · 2019-11-29 09:54:43Z

4

You can use a discriminated union type:

type SomeInterface = {
    variant?: 'single'
    value: number
} | {
    variant: 'multi',
    value: [number,number]
}

Playground Link

edited Nov 29, 2019 at 9:54

cubefox

1,32117 silver badges39 bronze badges

answered Nov 29, 2019 at 9:47

Titian Cernicova-Dragomir

253k37 gold badges464 silver badges394 bronze badges

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

Collectives™ on Stack Overflow

typescript set type depending on value

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related