TypeScript: narrow with `in` operator
typescripttyping
Use 'prop' in obj to narrow union types.
type A = { a: number } | { b: string };
function f(x: A) {
if ('a' in x) return x.a;
return x.b;
}Use 'prop' in obj to narrow union types.
type A = { a: number } | { b: string };
function f(x: A) {
if ('a' in x) return x.a;
return x.b;
}