Promises Tag

Node.js 16 available now

We are excited to announce the release of Node.js 16 today! Highlights include the update of the V8 JavaScript engine to 9.0, prebuilt Apple Silicon binaries, and additional stable APIs.

You can download the latest release from https://nodejs.org/en/download/current/, or use Node Version Manager on UNIX to install with nvm install 16. The Node.js blog post containing the changelog is available at https://nodejs.org/en/blog/release/v16.0.0.

Initially, Node.js 16 will replace Node.js 15 as our ‘Current’ release line. As per the release schedule, Node.js 16 will be the ‘Current’ release for the next 6 months and then promoted to Long-term Support (LTS) in October 2021. Once promoted to long-term support the release will be designated the codename ‘Gallium’.

As a reminder – Node.js 12 will remain in long-term support until April 2022, and Node.js 14 will remain in long-term support until April 2023. Node.js 10 will go End-of-Life at the end of this month (April 2021). More details on our release plan/schedule can be found in the Node.js Release Working Group repository.

V8 upgraded to V8 9.0

As always a new version of the V8 JavaScript engine brings performance tweaks and improvements as well as keeping Node.js up to date with JavaScript language features. In Node.js v16.0.0, the V8 engine is updated to V8 9.0 — up from V8 8.6 in Node.js 15.

This update brings the ECMAScript RegExp Match Indices, which provide the start and end indices of the captured string. The indices array is available via the .indices property on match objects when the regular expression has the /d flag.

> const matchObj = /(Java)(Script)/d.exec('JavaScript');
undefined
> matchObj.indices
[ [ 0, 10 ], [ 0, 4 ], [ 4, 10 ], groups: undefined ]
> matchObj.indices[0]; // Match
[ 0, 10 ]
> matchObj.indices[1]; // First capture group
[ 0, 4 ]
> matchObj.indices[2]; // Second capture group
[ 4, 10 ]

Stable Timers Promises API

The Timers Promises API provides an alternative set of timer functions that return Promise objects, removing the need to use util.promisify().

import { setTimeout } from 'timers/promises';
async function run() {
  await setTimeout(5000);
  console.log('Hello, World!');
}
run();

Added in Node.js v15.0.0 by James Snell (https://github.com/nodejs/node/pull/33950), in this release, they graduate from experimental status to stable.

Other recent features

The nature of our release process means that new features are released in the ‘Current’ release line approximately every two weeks. For this reason, many recent additions have already been made available in the most recent Node.js 15 releases, but are still relatively new to the runtime.

Some of the recently released features in Node.js 15, which will also be available in Node.js 16, include:

• Experimental implementation of the standard Web Crypto API
• npm 7 (v7.10.0 in Node.js v16.0.0)
• Node-API version 8
• Stable AbortController implementation based on the AbortController Web API
• Stable Source Maps v3
• Web platform atob (buffer.atob(data)) and btoa (buffer.btoa(data)) implementations for compatibility with legacy web platform APIs

New compiler and platform minimums

Node.js provides pre-built binaries for several different platforms. For each major release, the minimum toolchains are assessed and raised where appropriate.

Node.js v16.0.0 will be the first release where we ship prebuilt binaries for Apple Silicon. While we’ll be providing separate tarballs for the Intel (darwin-x64) and ARM (darwin-arm64) architectures the macOS installer (.pkg) will be shipped as a ‘fat’ (multi-architecture) binary.

The production of these binaries was made possible thanks to the generosity of MacStadium donating the necessary hardware to the project.

On our Linux-based platforms, the minimum GCC level for building Node.js 16 will be GCC 8.3. Details about the supported toolchains and compilers are documented in the Node.js BUILDING.md file.

Deprecations

As a new major release, it’s also the time where we introduce new runtime deprecations. The Node.js project aims to minimize the disruption to the ecosystem for any breaking changes. The project uses a tool named CITGM (Canary in the Goldmine), to test the impact of any breaking changes (including deprecations) on a large number of the popular ecosystem modules to provide additional insight before landing these changes.

Notable deprecations in Node.js 16 include the runtime deprecation of access to process.binding() for a number of the core modules, such as process.binding('http_parser').

For more information and to develop web applications using Node JS, Hire Node Developer from us as we give you a high-quality product by utilizing all the latest tools and advanced technology. E-mail us any clock at – hello@hkinfosoft.com or Skype us: “hkinfosoft”. To develop custom web apps using Node JS, please visit our Hire Node Developer technology page.

Content Source:

1. nodejs.medium.com

How Promises work in JavaScript

In the current age of JavaScript, Promises are the default way to handle asynchronous behavior in JavaScript. But how do they work? Why should you understand them very well?

A Promise in Real Life

When we make you a promise, you take our word that we will fulfill that promise.

But we don’t tell you when that promise will be fulfilled, so life goes on…

There are two possible scenarios: fulfillment or rejection.

Fulfillment

One day, we fulfill that promise. It makes you so happy that you post about it on Twitter!

Rejection

One day, we tell you that we can’t fulfill the promise.

You make a sad post on Twitter about how we didn’t do what we had promised.

Both scenarios cause an action. The first is a positive one, and the next is a negative one.

Keep this scenario in mind while going through how JavaScript Promises work.

When To Use a Promise

JavaScript is synchronous. It runs from top to bottom. Every line of code below will wait for the execution of the code above it.

But when you want to get data from an API, you don’t know how fast you will get the data back. Rather, you don’t know if you will get the data or an error yet. Errors happen all the time, and those things can’t be planned. But we can be prepared for it.

So when you’re waiting to get a result from the API, your code is blocking the browser. It will freeze the browser. Neither we nor our users are happy about that at all!

Perfect situation for a Promise!

How To Use a Promise

Now that we know that you should use a Promise when you make Ajax requests, we can dive into using Promises. First, we will show you how to define a function that returns a Promise. Then, we will dive into how you can use a function that returns a Promise.

Define a function with a Promise

Below is an example of a function that returns a Promise:

function doSomething(value) {
    return new Promise((resolve, reject) => {
        // Fake a API call
        setTimeout(() => {
            if(value) {
                resolve(value)
            } else {
                reject('The Value Was Not Truthy')
            }
        }, 5000)
    });
}

The function returns a Promise. This Promise can be resolved or rejected.

Like a real-life promise, a Promise can be fulfilled or rejected.

States

According to MDN Web Docs, a JavaScript Promise can have one of three states:

"- pending: initial state, neither fulfilled nor rejected.

- fulfilled: meaning that the operation was completed successfully.

- rejected: meaning that the operation failed."

Pending

The pending state is the initial state. This means that we have this state as soon we call the doSomething() function, so we don’t know yet if the Promise is rejected or resolved.

Resolved

In the example, if the value is truthy, the Promise will be resolved. In this case, we pass the variable value in it to use it when we would call this function.

We can define our conditions to decide when to resolve our Promise.

Rejected

In the example, if the value is falsy, the Promise will be rejected. In this case, we pass an error message. It’s just a string here, but when you make an Ajax request, you pass the server’s error.

Use a Function With a Promise

Now that we know how to define a Promise, we can dive into how to use a function that returns a Promise:

// Classic Promise
doSomething().then((result) => {
    // Do something with the result
}).catch((error) => {
    console.error('Error message: ', error)
})
// Use a returned `Promise` with Async/Await 
(async () => {
    let data = null
    try {
        data = await doSomething()
        // Do something with the result
    } catch(error) {
        console.error('Error message: ', error)
    }
})();

You can recognize a function that returns a Promise by the .then() method or an await keyword. The catch will be called if there is an error in your Promise. So making error handling for a Promise is pretty straightforward.

Promises are used in a lot of JavaScript libraries and frameworks as well. But the simplest web API is the Fetch API, which you should use for making Ajax requests.

For more information and to develop your web app using front-end technology, Hire Front-End Developer from us as we give you a high-quality solution by utilizing all the latest tools and advanced technology. E-mail us any clock at – hello@hkinfosoft.com or Skype us: “hkinfosoft“. To develop your custom website using JS, please visit our technology page.

Content Source:

1. betterprogramming.pub