TYPESCRIPT

typescript property does not exist on union type

type Fish = { swim: () => void };
type Bird = { fly: () => void };
 
function move(animal: Fish | Bird) {
  if ("swim" in animal) {
    return animal.swim();
  }
 
  return animal.fly();
}
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union type property does not exist

import { is } from 'typescript-is';

...

const getText = (obj: Obj1 | Obj2): string => {
  if (is<Obj1>(obj)) {
    return obj1.message;
  }

  return obj2.text;
};