I have this enum
enum OfferType {
Apartment = 'apartment',
House = 'house',
Room = 'room',
Hotel = 'hotel',
}
Which of the options should be used, when you type the value of the property. When to apply each approach
1)
{
type: type as OfferType
}
{
type: OfferType[type as 'apartment' | 'house' | 'room' | 'hotel']
{
I'm going to assume that type is of type string because you're receiving it from something outside the scope of your TypeScript code.
In that case, I wouldn't use either option you've shown, because they both assume that type is a valid OfferType, and that's not a reliable assumption. (But if you want to make that assumption, there's no reason for #2, just use #1; playground link.)
Instead, I'd use either a type predicate function or a type assertion function, which both narrow the type of type to OfferType and check that assumption at runtime.
Type predicate:
function isOfferType(value: string): value is OfferType {
return (Object.values(OfferType) as string[]).includes(value);
}
Usage:
if (isOfferType(type)) {
obj = { type };
} else {
// Handle the fact it isn't one
Type assertion function:
function assertIsOfferType(value: string): asserts value is OfferType {
if (!(Object.values(OfferType) as string[]).includes(value)) {
throw new Error(`"${value}" is not a valid OfferType`);
}
}
Usage:
assertIsOfferType(type);
const obj = { type };