What is an executor function for a Javascript promise?

DanielNovember 23, 2021November 26, 2021

We can pass an executor function to the constructor of a Javascript native promise. It takes two parameters: the resolve and rejects callouts of that promise:

new Promise( 
    () => {...} 
).then ( ... );

Based on our needs we can customize the behavior of that Promise using the exector.

For example, we can have for this executor function to automatically trigger the resolve or the rejects if our promise does not get an answer after some amount of time.

const executor = (resolve, reject) => {
    setTimeout(
        () => reject("Did not get an anwser after 1 sec")
    , 1000);
};

// this promise will automatically be rejected after 1 sec
new Promise(executor).then(result => {
    console.log(result);
});

More details about it here.