Skip to content
FrontendHaltFrontendHalt
JavaScript·Intermediate·Coding·1 min read

Are promise handlers synchronous when the promise is already fulfilled?

Short interview answer

No. then, catch, and finally handlers run asynchronously as promise jobs, typically represented as microtasks in browser explanations. This consistent behavior prevents a function from sometimes calling back synchronously and sometimes later.

Example

JavaScript
console.log('start');Promise.resolve().then(() => console.log('then'));console.log('end');
// start  end  then  — the handler always waits for the current task

Key takeaway

Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.

← Back to Promises

Related questions