A promise is an object that may produce a single value some time in the future: either a resolved value, or a reason that it’s not resolved (e.g., a network error occurred).
The function passed to new Promise is called the executor. When the promise is created, this executor function runs automatically. It contains the producing code, that should eventually produce a result.
The resulting promise object has internal properties:
state — initially PENDING, then changes to either FULFILLED or REJECTED,
an array of the functions we need to call once this promise is settled.
result — an arbitrary value of your choosing, initially undefined.
When the executor finishes the job, it should call one of the functions that it gets as arguments:
resolve(value) — to indicate that the job finished successfully:
sets state to “fulfilled”,
sets result to value.
reject(error) — to indicate that an error occurred:
sets state to “rejected”,
sets result to error.
git clone https://github.com/nishammahsin/my-own-js-promise.git
cd my-own-js-promise
npm install or yarn
MyPromise = require("./index")
eg:
let promise = new MyPromise(resolve => { setTimeout(() => resolve('My promise'), 100); }); p.then(res => console.log(res));
yarn run test