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typescript as operator

Marcel Tauber answered on September 26, 2022 Popularity 8/10 Helpfulness 1/10

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typescript as operator

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/* 
User-Defined Type Guards
It would be much better if once we performed the check,
we could know the type of pet within each branch.

It just so happens that TypeScript has something called a type guard.
A type guard is some expression that performs a runtime check 
that guarantees the type in some scope.

Using type predicates
To define a type guard, we simply need to define a function 
whose return type is a type predicate:
*/

function isFish(pet: Fish | Bird): pet is Fish {
  return (pet as Fish).swim !== undefined;
}

Popularity 8/10 Helpfulness 1/10 Language typescript

Source: www.typescriptlang.org

Tags: as-operator typescript

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Contributed on Sep 26 2022

Marcel Tauber

0 Answers Avg Quality 2/10

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typescript as operator

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let pet = getSmallPet();
let fishPet = pet as Fish;
let birdPet = pet as Bird;
 
if (fishPet.swim) {
  fishPet.swim();
} else if (birdPet.fly) {
  birdPet.fly();
}
//Example of code working via property accessors, using type assertion

Popularity 8/10 Helpfulness 1/10 Language typescript

Source: www.typescriptlang.org

Tags: as-operator typescript

Link to this answer
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Contributed on Sep 26 2022

Marcel Tauber

0 Answers Avg Quality 2/10

typescript as operator

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