The any And unknown Types

any

In TypeScript, the “any” type is a type that allows for any value. This means that when you declare a variable with the “any” type, you can assign it a value of any type without getting a type error from the TypeScript compiler. For example:
let myVariable: any = "hello";
myVariable = 10;
In this example, the myVariable variable is initially declared with the “any” type and assigned the string value “hello”. Later, the value of myVariable is changed to the number 10, which is allowed because myVariable has the “any” type.
The “any” type is often useful when migrating a codebase from JavaScript to TypeScript, as it allows you to gradually add type annotations to your code without breaking it. When migrating a large codebase, it can be difficult to add type annotations to every variable and function right away, so using the “any” type can help you make the transition more smoothly.
However, it’s generally considered best practice to use the most specific type possible for a variable, as this can help prevent type errors and make your code easier to understand. Once you have finished migrating your code to TypeScript, you should go back and update any “any” type declarations to use more specific types.

unknown

The “unknown” type is a type that is more strict than the “any” type. While variables of the “any” type can be assigned values of any type without causing a type error, variables of the “unknown” type can only be assigned values of the “unknown” type, or values of any type if the type is checked at runtime.
Type checking in TypeScript happens during compilation, not at runtime. This means that the TypeScript compiler will check the types of your variables and functions to ensure they are correct, and will give you an error if they are not. Using the “unknown” type allows you to delay type checking until runtime, so you can ensure that the value of a variable is of the correct type before using it in your code.
A real-life example of using the “unknown” type could be when working with data that comes from an external source, such as an API call. If the structure of the data returned by the API is not known at compile time, you could declare a variable with the “unknown” type to store the data, and then use type checking at runtime to ensure that the data has the correct structure before using it in your code.
Here’s an example of how you could use the “unknown” type in this scenario:
let data: unknown;
// make an API call and store the result in the 'data' variable
if (typeof data === "object" && data.hasOwnProperty("name") && data.hasOwnProperty("age")) {
  // the 'data' variable has the correct structure, so we can use it
  console.log(`Name: ${data.name}, Age: ${data.age}`);
} else {
  // the 'data' variable does not have the correct structure, so we cannot use it
  console.log("Invalid data received from API");
}
In this example, the data variable is declared with the “unknown” type, and the API call is assumed to return data in an object with a “name” and “age” property. At runtime, the code checks the structure of the data variable to ensure it has the correct properties, and only uses the data if it does. This prevents type errors and helps ensure that the code is working with valid data.