A callback result that is known to complete synchronously.
The engine ignores this value. Primitive and non-thenable object returns are
accepted so idiomatic expression-bodied callbacks remain valid; Promise and
thenable returns are rejected by both TypeScript and the runtime boundary.
A callback result that is known to complete synchronously.
The engine ignores this value. Primitive and non-thenable object returns are accepted so idiomatic expression-bodied callbacks remain valid; Promise and thenable returns are rejected by both TypeScript and the runtime boundary.