I am currently working on creating a versatile type that accurately represents the structure of a C union value in TypeScript. To illustrate, consider this initial type definition:
type UserIdentifier = {
id: string;
dateCreated: string;
names: {
first: string;
last: string;
}
};
After some modifications, the type should transform into the following format:
type UserIdentifier = {
id: string;
dateCreated?: undefined;
names?: undefined;
} | {
id?: undefined;
dateCreated: string;
names?: undefined;
} | {
id?: undefined;
dateCreated?: undefined;
names: {
first: string;
last: string;
};
};
The explicit inclusion of undefined for other properties as well as making them optional is necessary because TypeScript does not issue errors if there are additional properties in one part of the union that were not present in the original declaration. This behavior can be seen in the following example:
const f: { first: string; } | { last: string; } = { first: "hey", last: "you" };