I want an array that allow only for the value of 'john' and 'james', both are not required, I tried below interface:
interface User {
name: ['john' | 'james']
}
but it doesn't work for
const user: User = ['john', 'james']
it work only
const user: User = ['john']
const user: User = ['james']
I think I missed something
You have typed an array with exactly one element that can either be john or james. If you want to allow multiple elements, you will need to do:
interface User {
name: ('john' | 'james')[]
}
Now all the following are valid:
const u1: User = {
name: ['john']
};
const u2: User = {
name: ['james']
};
const u3: User = {
name: ['john', 'james']
};
If the use of an interface is not mandatory, you can take advantage of union types:
type User = 'john' | 'james';
const user1:User[] = ['john', 'james', 'jane'];
// ----------------------------------> ~~~~~~
// Type '"jane"' is not assignable to type 'User'.(2322)
const user2:User[] = ['john', 'james', 'james']; // No errors
nameproperty that is required by the interface.