https://github.com/theiyd/promnom

🛠 A custom implementation of Javascript Promises
https://github.com/theiyd/promnom

javascript promises

Last synced: 3 days ago
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🛠 A custom implementation of Javascript Promises

• Host: GitHub
• URL: https://github.com/theiyd/promnom
• Owner: theIYD
• License: mit
• Created: 2020-07-08T12:12:41.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2022-12-30T20:55:37.000Z (almost 2 years ago)
• Last Synced: 2024-05-16T01:02:35.987Z (6 months ago)
• Topics: javascript, promises
• Language: JavaScript
• Homepage:
• Size: 150 KB
• Stars: 2
• Watchers: 3
• Forks: 0
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        


## promnom

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[![GitHub license](https://img.shields.io/github/license/theIYD/promnom)](https://github.com/theIYD/promnom/blob/master/LICENSE)

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A custom implementation of Javascript promises from scratch. The purpose of this implementation was to deeply understand how promises allow asynchronous operations using `setTimeout()` Web API & how a data structure like a queue is maintained.

### Background

A promise represents the eventual result of an asynchronous operation. The primary way of interacting with a promise is through its `then` method, which registers callbacks to receive either a promise’s eventual value or the reason why the promise cannot be fulfilled.

### Usage

```js

const Promnom = require("./index");

const fs = require("fs");

const path = require("path");

const readFile = (filename, enc) =>

  new Promnom((resolve, reject) => {

    fs.readFile(filename, enc, (err, value) => {

      if (err) {

        return reject(err);

      }

      resolve(value);

    });

  });

const delay = (time, value) =>

  new Promnom((resolve) => {

    setTimeout(() => {

      resolve(value);

    }, time);

  });

readFile(path.join(__dirname, "index.js"), "utf-8")

  .then((text) => {

    console.log(`${text.length} characters read`);

    return delay(2000, text.replace(/[aeiou]/g, ""));

  })

  .then((newText) => {

    console.log(newText.slice(0, 200));

  })

  .catch((err) => {

    console.log("An error occurred");

    console.error(err);

  })

  .finally(() => {

    console.log("Promise done");

  });

/*

Output:

3472 characters read

cnst stts = rqr("./stts");

// Chck f  prms hs  thn mthd

cnst sThnbl = (mybPrms) =>

  mybPrms && typf mybPrms.thn === "fnctn";

// Glbl clss

clss Prmnm {

  cnstrctr(cmpt) {

    ths._stt = stts.PENDING

Promise done

*/

```

### License

MIT