JavaScript. What's new in ES2020?

As we discussed in our article about the ES2019 features you should try, ECMAScript's proposals will continue to grow and give rise to new implementations.

Therefore, you can already access the new ECMAScript features summarized in ES2020. So, in order not to miss the train, it is worth to be informed about these features.

Let's do it!

Dynamic import

Dynamic importing is one of the most interesting features of ES2020. It is a feature that you can use with lazy loading.

Previously if you wanted to import a module in JavaScript you would have something like the following:

import Math from ('./Math.js');
const Math = new Math;
Math.multiply();

The problem we had in this case, is that it was a static way of importing the Math module, and we could not delay the load if we wanted this module to depend on a user action.

Thanks to ES2020, you can now use lazy loading without a webpack! From now on you can use import as a function anywhere in your code, using an asynchronous function that returns a Promise.

The above code in ES2020 could be written as follows:

import Math from ('./Math.js');
.then((Math) => {
  const Math = new Math;
  Math.multiply();
});

Supported browsers: Chrome 63, Firefox 67, Opera 50, Safari 11.1

BigInt

Representing a number greater than 2^53-1 in JavaScript can be a problem, as it is the largest number that JavaScript can safely represent using the Number object.

The BigInt object is a native object that helps you represent numbers greater than 2^53-1. BigInt is interesting, therefore, if, for example, you want to do a multiplication of two numbers and there is a possibility of overflow. As the name "Int" indicates, you cannot use BigInt with a floating number.

const bigNumber = BigInt (90073498284849)
//90073498284849n

Supported browsers: Chrome 67, Firefox 68, Opera 54

Promise.allSettled

The Promise.allSettled() method returns a promise that resolves after all promises have either been resolved or rejected, with a vector of objects describing each promise's results.

In fact, Promise.allSettled(), looks like Promise.all(). But, as you well remember, Promise.all() waits for all promises to be fulfilled, or for any promise to be rejected.

Example

const promise1 = Promise.resolve(3);
const promise2 = new Promise((resolve, reject)=>
setTimeout (reject, 100, 'foo'));
const promise = [promise1, promise2];

Promise.allSettled(promises).
 then((results)=> results.foreach((result)=>
 console.log(result.status)));

//"fulfilled"
//"rejected"

Supported browsers: Chrome 76, Firefox 71, Safari 13, Node 12.1

globalThis

The property globalThis is good news! globalThis contains the global value this according to the context of the global object.

Thanks to globalThis you don't have to differentiate if the code is running in a browser (this), or in Node (global).

Example:

function canMakeHTTPrequest(){
      return typeof globalThis.XMLHttpRequest === 'function';
}

console.log(canMakeHTTPrequest());
//output in a browser:true

Supported browsers: Chrome 71, Firefox 65, Safari 12.1, Node 12

Conclusion

ES2020 has many other new features, interesting to try and perfect to help you improve your code by reducing verbosity. However, as you can see from the features we share today, not all of them are supported by all browsers. Especially the older browsers.

However, it is always worth taking a look, and play and practice with them, until they become standard.