Basics
TS unknown Type
Using the unknown Type
TypeScript unknown type is safer than any requiring type checks.
What is the unknown Type?
The unknown type in TypeScript is a top type, representing any value. It's similar to any, but with a significant difference: it is safer and enforces type checks before performing operations on the value. This ensures type safety and helps prevent runtime errors.
Differences Between unknown and any
While both unknown and any can hold any value, unknown requires a type check before you can perform most operations. This constraint encourages safer coding practices. In contrast, any allows you to perform operations without any checks, which could lead to errors if not used carefully.
Type Checking with unknown
When using unknown, you need to perform a type check to refine the type before using it. This can be done using typeof, instanceof, or custom type predicates. These checks ensure that the operations you perform are safe and valid for the given type.
When to Use unknown
Use unknown when you expect a value that can be of any type, but you want to enforce type safety before using it. This is particularly useful in scenarios where inputs come from dynamic sources like user input, JSON parsing, or API responses where the type is not known in advance.
Conclusion
The unknown type is a powerful tool in TypeScript for handling values of uncertain type while maintaining type safety. By requiring type checks before operations, it helps prevent runtime errors and encourages developers to write more robust code. Transitioning from any to unknown in your TypeScript projects can enhance code reliability and maintainability.
