I Have Very Good Feelings about ES2020 features

ES2020 has been out for a while. I guess a lot of Node developers have already adopted these features. Some even started using them when these features were still under proposal stages. Yep. My team started using some stage 3 features for quite a while.

In this article, I'm going to talk about my feelings of using these ES2020 features. As a result, I think those features are great and essential.

(Visit https://pitayan.com/posts/vue-techniques/ to read original article. Source code is highlighted.)

Contents:

• 1. Operator: Nullish Coalescing
• 2. Asychronous Modules: Dynamic import
• 3. Promise.allSettled
• 4. Very Large Number: BigInt
• 5. Regex: String.prototype.matchAll
• 6. A Standardized Global Object: GlobalThis
• 7. Chain with Elegance: Optional Chaining
• 8. Module Namespace Exports: export * as
• 9. Other features
  • for ... in loop order
  • import meta
• Conclusion
• References

1. Operator: Nullish Coalescing

At the beginning, my idea of "providing exlicit explanation of your code" denies such improvement. I think since a value of nullish or falsy should be given a thorough "explanation" under an if condition or some other strategic function. In this way, I could also add some extra logics without refactoring the shorthand expression later.

let website = {}

let url = 'https://pitayan.com'
if (website.url !== undefined && typeof website.url === String) {
  url = website.url
}

But I made compromise quickly after trying "nullish coalescing" everywhere in the project. My concern was proved unnecessary. Because what I want is to make sure the target variable has concrete value in most of the scenarios.

In Typescript, operating a nullish value will probably be given errors or warnings. This means my code can be optimized easily by following the expostulation.

let url: string = website.url ?? 'https://pitayan.com'

In brief, my feeling toward nullish coalescing is quite supportive. It' going to be very helpful while assigning non-nullable value to a variable.

2. Asychronous Modules: Dynamic import

I've been using this feature since stage 2. You know, our apps needs that ability of "Just in Time".

It helps me import Javascript / JSON files as modules in my application. And now it can just show up anywhere in my project (mostly for front end. Haven't experience it on server side). Have to say this feature is indispensible.

let answer = await import('./myanswer.json')

import('./component.js')
  .then(module => {
    module.default.mount(answer)
  })

3. Promise.allSettled

Promise.all has brought us a useful solution to the famous "callback hell". Nesting functions is truly nasty.

// Before
getUp().then(() => {
  washFace().then(() => {
    brushTeeth().then(() => {
      eatBreakfast()
    })
  })
})

// After
Promise.all([
  getUp,
  watchFace,
  brushTeeth
]).then(() => {
  eatBreakfast()
})

As you know, Promise.all will throw errors once one of the tasks encounters exceptions. I never hope that I can't eat breakfast without washing my face.

Of course, I can add finally to the Promise chain to make sure eating breakfast. But finally doesn't provide the correct context I wanted. Don't even have to mention using catch to eat breakfast, that's a bad practice.

Finally, allSettled permits us to set a callback whenever I wash my face or brush my teeth. I just want that breakfast! It feels like you grew up and move out of parents' home. So mom's scolding about washing face and brushing teeth are gone.

// Bad
Promise.all([
  getUp,
  watchFace,
  brushTeeth
]).then(() => {
  eatBreakfast()
}).catch(() => {
  eatBreakfast()
})

// Good
Promise.allSettled([
  getUp,
  watchFace,
  brushTeeth
]).then(results => {
  eatBreakfast()
})

4. Very Large Number: BigInt

The Javascript Number type used to range from -(2⁵³-1) to 2⁵³-1 (Number.MIN_SAFE_INTEGER ~ Number.MAX_SAFE_INTEGER).

With this new API, any large number can be process properly in browser without losing any precision.

let bitInteger = BitInt(9007199254740995)

// Or

let bitInteger = 9007199254740995n

In my case, big integers are converted into String to avoid precision issues before they are carried out to the front. It is indeed a rare case to use BitInt at the moment in my project. I believe there are other general demands around this features in other projects.

A simple example I can come up with is: If a database's model ID is numberic and fairly long (like a shopping order ID), then when it is passed onto the frontend the BigInt can come into help.

5. Regex: String.prototype.matchAll

Actually matchAll has been proposed for a long time. It returns an Array containing all matched characters. Compared to match, the return type RegExpStringIterator gives us a consistant result whenever the string matches or not. By using tools like Array.from I could finally pull all results from the iterator.

This after all is a good improvement in my humble opinion. Because the returned data type is always the same.

let url = 'https://pitayan.com'
let blank = ''
let reg = /pitayan.com/g

// match
url.match(reg) // ["pitayan.com"]
blank.match(reg) // null

// matchAll
Array.from(url.matchAll(reg)) // [["pitayan.com", index: 8, input: "https://pitayan.com", groups: undefined]]
Array.from(blank.match(reg)) // []

6. A Standardized Global Object: GlobalThis

Sometimes the JS code needs to cross platform, but Node.js uses global which is different to browser's window (web worker uses self). So before starting everything, I need to handle the environment compatibility first.

const globalThis = ((global, window, self) => {
  if (global) return global
  if (window) return window
  if (self) return self
  throw new Error('...')
})(global, window, self)

I personally think that identifying the environment is the duty of the lanuague system. So the globalThis is something that filled the nasty gap. Really really appreciated this feature's release.

7. Chain with Elegance: Optional Chaining

I've used this feature since stage 2. It helps reduce a lot of if conditions or ternary operators which made my code look much simpler.

let food = restuarant && restuarant.cooking && restuarant.cooking.food

// after
let food = restuarant?.cooking?.food

Other than accessing the properties, I can also use it on methods.

let food = restuarant?.cooking?().food

Isn't this looking good?

8. Module Namespace Exports: export * as

This an amazing API for Javascript. I used to export some modules in this way.

import A from './A.js'
import B from './B.js'
import C from './C.js'

export default { A, B, C }

Now I can do this instead.

export * as A from './A.js'
export * as B from './B.js'
export * as C from './C.js'

And the usage of import these modules stays the same.

import { A, B, C } from './index.js'

Fancy but very practical!

9. Other features

There are some other features I haven't experienced well enough to make conclusions. Their definition is clear enough to speculate the changes. I believe they are quite useful otherwise it's impossible to introduce them into the new standard.

for ... in loop order

The for in loop order wasn't specified by ECMAScript at the beginning. Each browsers has different behiviors but now they are unified aligning with the ECMA standard.

import meta

Now you can access the information from an imported module.

<script src="script.js"></script>

console.oog(import.meta) // { url: "https://pitayan.com/script.js" }

Conclusion

Javascript has brought us many convenient and powerful APIs these years. Our development has been improved ever since the new standards coming out continuously. And they are proved to be the life saver for us engineers. I wish there will be more powerful features in the future so that maybe one day I don't have to type any code to build a wonderful application.

Alright, that's all about some humble opitions toward the ES2020 features. I hope you also have the same feelings.

If you think this article is great, then please share it to the social network to let more people get involved.

Thank you for reading!

References

• https://www.freecodecamp.org/news/javascript-new-features-es2020/
• https://www.jianshu.com/p/416a0931e96c

---

Originally on Pitayan.com
https://pitayan.com/posts/es2020-features/

Comments

[pentacular]

I'm not much a fan of export *.

The reason is that what you export is unclear and depends on changes far away.

But the following pattern seems nice to me.

export { A, B, C } from './index.js';

[Yanze Dai]

I think "export *" is somewhat corresponding to "import *". Of course it's unclear in some cases but for files with only one default export it would be very helpful IMHO.