Mastering TypeScript 3 - Third Edition

Weak types

When an interface contains only optional properties, it is considered a weak type. In other words, if we create an object that implements a weak type interface, can we really say that the object implements the interface? Let's consider some code to find out, as follows:

interface IWeakType { 
    id?: number, 
    name?: string 
} 
 
let weakTypeNoOverlap: IWeakType; 
weakTypeNoOverlap = { description: "my description" }; 

Here, we have defined an interface named IWeakType that contains two properties, named id and name. As both of these properties are optional, this interface is considered to be a weak type. We then define a variable named weakTypeNoOverlap, and specify this object to be of type IWeakType. On the last line of this code, we assign ...