Why can I initialize friends below as an empty array [], but not do the same for session with an empty object {}? Is there a way to use the empty object without needing to make all keys optional in the interface?
const initialState: {
friends: Array<{
name: string;
age: number;
}>;
session: {
login: string;
avatar: string;
}
} = {
friends: [], // works fine
session: {} // results in an error!
};
Since the [] represents a valid array (with zero length) for the type
Array<{name:string;age:number;}>However, the curly braces {} do not form a valid object structure like {login: string; avatar: string}
When you have an object defined as let x = {} and then add a property with x.login = "name", you end up altering the structure of the object. Even if it is empty, it can still be considered an array of a specific type.
If you need an interface that can accept both empty objects {} and objects with specific properties like {login: string, avatar: string}, you can implement the following:
interface GenericObject {
[property: string]: any;
}
It's important to use this approach judiciously, as if your intention is to allow objects in any format, perhaps you wouldn't be specifying types in your code at all.
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