JavaScript · Senior · Question 3 of 75

Does the `new Promise(executor)` executor function run synchronously?

new Promise(() => console.log("A"));
console.log("B");

✓Correct answer: Yes: A is printed, then B
2No: B is printed, then A
3No: A isn't printed until resolve is called

Explanation

The executor is called right away in the constructor. Only then/catch/finally callbacks are asynchronous - they always run as microtasks, even if the promise is already settled. This guarantees a predictable code order.

Does the `new Promise(executor)` executor function run synchronously?

Explanation

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Does the new Promise(executor) executor function run synchronously?

Explanation

Further reading

Test yourself

Does the `new Promise(executor)` executor function run synchronously?