Basically a function can take either of these two types or param:
{a: string, b: number, c: SomeType}
{a: string, b: number, d: SomeOtherType}
I know I can write the type of the parameter as {a: string, b: number, c: SomeType} | {a: string, b: number, d: SomeOtherType}, but I'm trying to come up with something like:
{a: string, b: number} & ({c: SomeType} | {d: SomeOtherType})
So that I don't have to repeat the first two properties, is this possible?
You can define a type alias for the static properties and then use the intersection operator (&) to combine them with the optional union like this:
type StaticOptions = {
a: string;
b: number;
};
type Options = StaticOptions & (
{ c: boolean } | { d: null }
);
function fn (options: Options): void {}
Update in response to your comment:
You can define the exclusive properties as optional and never in each other's shape for "easier" DX:
type StaticOptions = {
a: string;
b: number;
};
type Options = StaticOptions & (
{
c: boolean;
d?: never;
}
| {
c?: never;
d: null;
}
);
function fn (options: Options): void {
const {
a, // string
b, // number
c, // boolean | undefined
d, // null | undefined
} = options;
}