The any and unknown Types
When you use the any type, you tell TypeScript to turn off type checking for that variable. This means you can assign any value to it and perform any operation, but you lose all benefits of type safety.
On the other hand, the unknown type is safer. Like any, you can assign any value to a variable of type unknown. However, you cannot use the value in operations until you perform a type check. TypeScript forces you to check the type before using it, which helps prevent errors.
1234567891011121314151617let valueAny: any = "Hello"; let valueUnknown: unknown = "World"; // You can assign any value to a variable of type any or unknown valueAny = 42; valueUnknown = 42; // You can perform any operation on a value of type any console.log(valueAny.toFixed(2)); // No error at compile time // But you cannot perform operations on unknown without type checking // console.log(valueUnknown.toFixed(2)); // Error: Object is of type 'unknown' // To use valueUnknown safely, you must first check its type if (typeof valueUnknown === "number") { console.log(valueUnknown.toFixed(2)); }
In the example above, valueAny can be used in any way, and TypeScript will not warn you about possible mistakes. This can lead to runtime errors that TypeScript cannot catch.
In the example, trying to call toFixed on valueUnknown causes a compile-time error unless you first check that it is a number.
You should use unknown instead of any when you do not know the type of a value ahead of time, but want to make sure you check it before using it. This keeps your code safer and more predictable.
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Can you explain more differences between `any` and `unknown`?
When should I use `any` instead of `unknown`?
Can you give more examples of using `unknown` safely?
Awesome!
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When you use the any type, you tell TypeScript to turn off type checking for that variable. This means you can assign any value to it and perform any operation, but you lose all benefits of type safety.
On the other hand, the unknown type is safer. Like any, you can assign any value to a variable of type unknown. However, you cannot use the value in operations until you perform a type check. TypeScript forces you to check the type before using it, which helps prevent errors.
1234567891011121314151617let valueAny: any = "Hello"; let valueUnknown: unknown = "World"; // You can assign any value to a variable of type any or unknown valueAny = 42; valueUnknown = 42; // You can perform any operation on a value of type any console.log(valueAny.toFixed(2)); // No error at compile time // But you cannot perform operations on unknown without type checking // console.log(valueUnknown.toFixed(2)); // Error: Object is of type 'unknown' // To use valueUnknown safely, you must first check its type if (typeof valueUnknown === "number") { console.log(valueUnknown.toFixed(2)); }
In the example above, valueAny can be used in any way, and TypeScript will not warn you about possible mistakes. This can lead to runtime errors that TypeScript cannot catch.
In the example, trying to call toFixed on valueUnknown causes a compile-time error unless you first check that it is a number.
You should use unknown instead of any when you do not know the type of a value ahead of time, but want to make sure you check it before using it. This keeps your code safer and more predictable.
Grazie per i tuoi commenti!
