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'any' vs 'unknown' in TypeScript πŸ‘€

Karishma
・Updated on ・2 min read

When you start learning TypeScript, you will come across two types - any and unknown.
Today, I will try to explain the difference between the two in the simplest way possible.

any - The any type allows us to assign literally β€œany” particular value to that variable, simulating what we know as plain JavaScript.

unknown - The unknown type is the type-safe counterpart of any. Anything is assignable to unknown, but unknown isn't assignable to anything but itself and any without a type assertion or a control flow based narrowing.

Errghh... Let's understand with an example.

let age: number;
let userAge: any;

userAge = 'This is some age';
userAge = 20;

age = userAge;
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And yes, This code works! πŸŽ‰ Type of userAge is any so it can be assigned any value - string, number etc.

let age: number;
let userAge: unknown;

userAge = 'This is some age';
userAge = 20;

age = userAge;
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The statement age=userAge gives an error. I mean, the type is unknown so what is the problem here? To assign an unknown value to a value with a fixed type, we have to do some quick type check!

let age: number;
let userAge: unknown;

userAge = 'This is some age';
userAge = 20;

if(typeof userAge === 'number') {
  age = userAge;
}
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And now this works too! πŸŽ‰

When to use what? πŸ€”
Honestly speaking you shouldn't use either of them. But if you really really have to then unknown is a better choice if you know what you want to do with that value eventually.
I don't recommend using any - it takes away the actual essence of TypeScript!

I hope you learnt at least something. Also, this was my first ever post on Dev! Thank you for reading :)

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