promise-plus-callback
Make a callback-based or promise-based functions to support both promises and callbacks. Uses the native promise implementation. with typescript support.
Installation
npm i promise-plus-callback
Import or Require
import ppc from "promise-plus-callback";
OR
import {fromCallback,fromPromise} from "promise-plus-callback";
OR
const ppc = require("promise-plus-callback");
OR
const fromCallback = require("promise-plus-callback");
OR
const fromPromise = require("promise-plus-callback");
fromCallback
function:
Here is an example usage of Suppose you have an asynchronous function readFile that reads a file and takes a callback as the last argument:
function readFile(filename, callback) {
// Asynchronous operation to read file
}
You can convert this function to return a Promise with fromCallback
function as follows:
import {fromCallback} from "promise-plus-callback";
const readFilePromise = fromCallback(readFile);
// You can now call the function with a Promise:
readFilePromise(filename)
.then((data) => console.log(data))
.catch((err) => console.error(err));
// Or with a callback:
readFilePromise(filename, (err, data) => {
if (err) {
console.error(err);
} else {
console.log(data);
}
});
This allows you to use the same function in either Promise-based or callback-based code.
fromPromise
function:
Here is an example usage of Suppose we have a function getUser that returns a promise:
function getUser(userId) {
return new Promise((resolve, reject) => {
// some async operation to fetch user
setTimeout(() => {
if (userId === '123') {
resolve({ id: '123', name: 'John Doe' });
} else {
reject(new Error('User not found'));
}
}, 100);
});
}
We can use fromPromise
to create a function that can be called with a callback:
import {fromPromise} from "promise-plus-callback";
const getUserCallback = fromPromise(getUser);
getUserCallback('123', (err, user) => {
if (err) {
console.error(err);
} else {
console.log(user); // { id: '123', name: 'John Doe' }
}
});
In the above example, the getUserCallback function accepts a callback as its last argument. If a callback is provided, it calls the original getUser function with the provided arguments and passes the result or error to the callback. If no callback is provided, it returns a promise.
We can also call getUserCallback without a callback to get a promise:
getUserCallback('123')
.then(user => console.log(user)) // { id: '123', name: 'John Doe' }
.catch(err => console.error(err));
License
promise-plus-callback is licensed under the MIT License.