What’s New in Node.js 15

Details of Node.js 15 new features, including throw on unhandled rejections and V8 8.6 language features

Image credit: Author

Node.js 15 was released October 20, 2020. It comes with a number of major features:

• Throw on unhandled rejections
• V8 8.6 language features
• NPM 7
• Experimental support for QUIC
• N-API Version 7
• Refinement of the Async Local Storage APIs

Let’s explore what they are and how to use them.

Use NVM to Explore Node

In a previous article, we provided instructions on using NVM (Node Version Manager) to manage Node.js and NPM versions. In our environment, we had Node.js 12.16.0 and NPM 6.14.8 installed. By running nvm install node, we installed Node.js 15.4.0 and NPM7.0.15.

We have two windows open, one is set to Node.js 12, and the other one is set to Node.js 15.

On the node12 window:

$ nvm use 12
Now using node v12.16.0 (npm v6.14.8)

On the node15 window:

$ nvm use 15
Now using node v15.4.0 (npm v7.0.15)

Now we’re ready to explore.

Throw On Unhandled Rejections

The unhandledRejection event is emitted whenever a promise is rejected and no error handler is attached to the promise within a turn of the event loop. Starting from Node.js 15, the default mode for unhandledRejection has been changed to throw from warn. In throw mode, if an unhandledRejection hook is not set, the unhandledRejection is raised as an uncaught exception.

Create a program so that a promise is rejected with an error message:

When you run this code on node12 window it shows a long warning message:

$ node myPromise.js
(node:79104)…