I have an object property with the following signature.
handleItem = (data: Output & { isValid: boolean }) => {}
I do not understand the & part.
Basically I trying to pass some arguments as:
handleItem (outputItem, { isValid: false })
and I receive an error
Expected 1 arguments, but got 2.'
How to pass values property? How the & is used in this instance?
handleItem takes a single argument, an object that has the properties of Output and the isValid property. You need to construct such an object. Using the spread operator is a good option:
handleItem ({ isValid: false, ...outputItem })
You can read more about intersection types here
this is called Intersection Type and it means that your param of your handleItem() method combines Output and { isValid: boolean } - will say that your parameter needs to have both types, Output and { isValid: boolean }.
so you need to call it this way:
handleItem ({ isValid: false, ...outputItem })
if you want to pass two parameters do the following:
handleItem = (data: Output, { isValid: boolean }) => {}
afterwards you can do:
handleItem (outputItem, { isValid: false })
& is a type intersection. Output & { isValid: boolean } means it expects something as argument that conforms both to the interface Output and { isValid: boolean }. In other words, it expects one object which has an isValid property and whatever else Output defines.
I think the syntax expect the property isValid of data to be boolean
& { isValid: boolean }is describing thedata: Outputpart. This makes sense, considering there should be one argument.:is a type annotation. The function only takes a single object as argument. (And that object needs to contain anisValidproperty.)