Type widening is usually implicit, meaning that it is performed by TypeScript, because it involves moving from a narrow category to a broader one. Type widening, or upcasting, occurs when you need to convert a variable from a subtype to a supertype. Type casting comes in handy when you need to treat an object of a particular subtype as its supertype or vice versa. A supertype, on the other hand, is a more general type that is the basis of multiple subtypes.Ĭonsider a scenario where you have a class hierarchy with a superclass called “Animal” and two subclasses named “Cat” and “Dog.” Here, “Animal” is the supertype, while “Cat” and “Dog” are the subtypes. Generally, a subtype is a specialized version of a supertype that inherits the supertype’s attributes and behaviors. One way to classify types is to split them into sub- and supertypes. But before you can start using type casting effectively, you’ll need to understand some foundational concepts like subtype and supertype relationships, type widening, and type narrowing. Type casting is essential for performing various operations, including arithmetic calculations, and data, manipulation, and compatibility checks. Implicit casting occurs when TypeScript sees a type error and attempts to safely correct it. Type casting can happen in one of two ways: it can be implicit, which is when TypeScript handles the operation, or explicit, when the developer handles the conversion.
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