Use unknown over any in Typescript

unknown is the type-safe variant of any. Both allow any values to be assigned to them, but unknown isn't assignable to anything, where as any is. This means that to use a variable of type unknown, it requires a type assertion or narrowing to a more specific type first.

Essentially this can be any value, but you must perform a type check before using it. As a blanket rule, every any should be replaced with an unknown.

let vAny: any = 10;          // We can assign anything to any
let vUnknown: unknown =  10; // We can assign anything to unknown just like any 


let s1: string = vAny;     // Any is assignable to anything 
let s2: string = vUnknown; // Invalid we can't assign vUnknown to any other type (without an explicit assertion)

vAny.method();     // ok anything goes with any
vUnknown.method(); // not ok, we don't know anything about this variable

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