Unknown type in typescript

The unknown type in typescript is a common type that you will likely to come across. It is a strict version of the any type and in terms of accepting data, it accepts any data type which is similar to nature of any type. However there is a minor differences between them. Since an unknown type also can have multiple type, it forces to use type assertion before using the types function. To further clear , lets look an example

 function readAny(val: any){
     return val.trim();
}

In the above example, we are using any type for the value. Since trim is a string function, this works well for string data. However on supplying numbers or booleans , we get a runtime error

The same example using unknown

 function readAny(val: unknown){
     return val.trim(); // typescript error at this line
}

Typescript would throw a compile time error as we are using string function without type assertion. To fix it, the correct code would look like

 function readAny(val: unknown){

    if( typeof val === 'string')
     return val.trim();
}

Conclusion

The unknown type in TypeScript provides a safe alternative to any, offering type safety while still allowing flexibility in dynamic programming. When a value is of type unknown, it forces developers to perform type checks before using the value, reducing the risk of runtime errors. This encourages more deliberate and safer code practices compared to any, which bypasses type checking. The unknown type is particularly useful in scenarios involving user input or third-party APIs, where the exact type may not be known at compile-time, making it a vital tool for maintaining type safety in uncertain conditions.