2) Nullish Coalescing Operator:
3) Optional Chaining:
Promise.allSettled() accepts an array of promises and will return the data from the promises regardless of whether the promise is resolved or rejected. It will wait until the promises finishes their execution and once the promise executes it will return the data. Below is the example of Promise.allSettled().
React 17 Features
There are no major developer facing features added to React 17, instead this version is primarily focused on making it easier to upgrade React itself
As mentioned in the React Docs
In React 17, React will no longer attach event handlers at the document level, instead it will attach the event handler to the root DOM container into which the react tree is rendered
What it means is that react will not attach the events to the html document as it does in the previous versions, instead it will attach those event handlers to the root div element where our React App gets rendered.
React 17 will also provide support for the new version of JSX transform. With the new JSX transform, you can still use JSX without importing React in your application.