Check if object got at least specified properties

user_7008628 0
Viewed 56

I have a function that send an object that got { name: { value: string }, + some unknown property }, how can I type my parameter to accept this object if he got at least { name: { value: string } } ?

Example:

// Working but is there a specific type to explicitly do this without [x:string]: any ?
const sortNameV2 = (array: Array<{ name: { value: string }, [x:string]: any }>, sortOrder: 'ASC' | 'DESC') => {
  return [...array]
    .sort((a, b) => 
      a.name.value.localeCompare(b.name.value)
    )
}

sortNameV2([{ name: { value: 'titi'}, id: 1 }], 'ASC')
typescript
2 Answers

Make it a generic type argument using extends:

// Working but is there a specific type to explicitly do this without [x:string]: any ?
const sortNameV2 = <ElementType extends { name: { value: string } }>(array: Array<ElementType>, sortOrder: 'ASC' | 'DESC') => {
//                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^−−−−−−−−−−−−−^^^^^^^^^^^^^
  return [...array]
    .sort((a, b) => 
      a.name.value.localeCompare(b.name.value)
    )
}

sortNameV2([{ name: { value: 'titi'}, id: 1 }], 'ASC')

Playground link

user_1572470

Not answering your question directly.

Working with generics might get confusing. My suggestion is that you do not create a function that sorts the array but rather just the comparer. Maybe it would be more reusable, because it allows the user to decide whether to create a copy or to sort in place. Also you could wrap it in a curried function that gets passed a sort order.

type ItemWithName = { name: { value: string }}

const sortNameComparer(order: 'ASC' | 'DESC' = 'ASC') {
   return (a: ItemWithName, b: ItemWithName) => 
        a.name.value.localeCompare(b.name.value) * (
           order === 'ASC' ? 1 : -1
        )
}

// usage

[{ name: { value: 'titi'}, id: 1 }].sort(sortNameComparer('ASC'))
user_19560720
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