This content originally appeared on DEV Community and was authored by Karishma
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 “any” 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;
And yes, This code works! ? 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;
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;
}
And now this works too! ?
When to use what? ?
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 :)
This content originally appeared on DEV Community and was authored by Karishma
Karishma | Sciencx (2021-07-05T19:50:08+00:00) ‘any’ vs ‘unknown’ in TypeScript ?. Retrieved from https://www.scien.cx/2021/07/05/any-vs-unknown-in-typescript-%f0%9f%91%80/
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