The 7 most transformative JavaScript features from ES10

Last updated on March 08, 2024

JavaScript has come a long way in the past 10 years with brand new feature upgrades in each one.

Still remember when we created classes like this?

function Car(make, model) {
  this.make = make;
  this.model = model;
}

// And had to join strings like this
Car.prototype.drive = function() {
  console.log("Vroom! This " + this.make +
    " " + this.model + " is driving!");
};

Yeah, a lot has changed!

Let's take a look at the 7 most significant features that arrived in ES10 (2019); and see the ones you missed.

1. Modularization on the fly: Dynamic `import`s

The ES10 year was the awesome year when import could now act as function, like require(). An async function.

Keeping imports at the top-level was no longer a must; We could now easily resolve the module's name at compile time.

Loading modules optionally and only when absolutely needed for high-flying performance...

async function asyncFunc() {
  if (condition) {
    const giganticModule = await import('./gigantic-module');
  }
}

Loading modules based on user or variable input...

import minimist from 'minimist';

const argv = minimist(process.argv.slice(2));

viewModule(argv.name);

async function viewModule(name) {
  const module = await import(name);
  console.log(Object.keys(module));
}

It's also great for using ES modules that no longer support require():

// ❌ require() of ES modules is not supported
const chalk = require('chalk');
console.log(chalk.blue('Coding Beauty'));

(async () => {
  // ✅ Runs successfully
  const chalk = (await import('chalk')).default;
  console.log(chalk.blue('Coding Beauty'));
})();

2. Flattening the curve

flat() and flatMap() gave much cleaner ways to easily flatten multidimensional arrays.

Eradicating the need for painful array-looping flattening code:

const colorSwatches = [
  'cream🟡',
  ['scarlet🔴', 'cherry🔴'],
  ['blue🔷', ['sky blue🟦', 'navy blue🔵']],
];

// Default depth of 1
console.log(colorSwatches.flat());
// ['cream🟡', 'scarlet🔴', 'cherry🔴', 'blue🔷',
//   ['sky blue🟦', 'navy blue🔵']]

console.log(colorSwatches.flat(2));
// ['cream🟡', 'scarlet🔴', 'cherry🔴', 'blue🔷',
//   'sky blue🟦', 'navy blue🔵']

flatMap() is as good as calling map(), then flat(1):

const colorSwatches = [
  'cream🟡',
  ['scarlet🔴', 'cherry🔴'],
  ['blue🔷', ['sky blue🟦', 'navy blue🔵']],
];

// map to get only the emoji
console.log(
  colorSwatches.flatMap((color) =>
    Array.isArray(color) ? color : color.slice(-2)
  )
);
// [ '🟡', 'cherry🔴', 'blue🔷', [ 'sky blue🟦', 'navy blue🔵' ] ]

3. Transform arrays to objects

ES10 was also when Object.fromEntries() arrived on the JavaScript scene.

Quickly convert list of key-value pairs to equivalent key-value object:

const entries = [
  ['name', 'The Flash⚡'],
  ['realName', 'Barry Allen'],
  ['lightningColor', 'yellow🟡'],
  ['suitColor', 'red🔴'],
];

console.log(Object.fromEntries(entries));
/**
{
  name: 'The Flash⚡',
  realName: 'Barry Allen',
  lightningColor: 'yellow🟡',
  suitColor: 'red🔴'
}
*/

4. Clean up your strings with precisions

trimStart() and trimEnd().

Before now everyone was using trim from NPM - Happily adding 3.35KB to the project...

Even now:

But slowly losing popularity to .trim().

Then Array trim() came along, then trimStart() and trimEnd().

const fruits = '   pineapple🍍   ';

console.log(fruits.trimStart()); // 'pineapple🍍   '

console.log(fruits.trimEnd()); // '   pineapple🍍'

console.log(fruits.trim()); // 'pineapple🍍'

5. Catching errors without the baggage

With the new optional catch binding, you now safely omit the catch block's error argument when you had nothing to do with it:

// ❌ Before ES10
try {
  iMayExplodeAnyMomentNow();
} catch (err) {
  // Or else error
}

// ✅
try {
  iMayExplodeAnyMomentNow();
} catch {}

6. Sorting without surprise

Stable Array sort.

Previously when sorting an array there was absolutely no way we could guarantee the arrangement of the equal elements.

But in the post-ES10 JS code here, we are 100% sure that react always comes before vue always comes before angular.

const geniusPortfolio = [
  {
    tool: 'javascript',
    years: 2000,
  },
  { tool: 'react', years: 1000 },
  { tool: 'vue', years: 1000 },
  { tool: 'angular', years: 1000 },
  { tool: 'assembly', years: 7000 },
];

const sortedDesc = geniusPortfolio.sort((a, b) => {
  return b.years - a.years;
});

const sortedAsc = geniusPortfolio.sort((a, b) => {
  return a.years - b.years;
});

7. Go big or go home: `BigInt`s

The name BigInt gives it purpose away: For loading up on unbelievably humongous integer values:

const bigInt =
  240389470239846028947208942742089724204872042n;

const bigInt2 = BigInt(
  '34028974029641089471947861048917649816048962'
);

console.log(typeof bigInt);
console.log(bigInt);

console.log(typeof bigInt2);
console.log(bigInt2);

console.log(bigInt * bigInt2);

Because normal integers can't:

// ✖️ Stored as double
const normalInt = 240389470239846028947208942742089724204872042;

const normalInt2 = 34028974029641089471947861048917649816048962;

console.log(typeof normalInt);
console.log(normalInt);

console.log(typeof normalInt2);
console.log(normalInt2);

// ✖️ Precision lost
console.log(normalInt * normalInt2);

Final thoughts

ES10 marked a significant leap forward for JavaScript with several features that have become essential for modern development.

Use them write cleaner code with greater conciseness, expressiveness, and clarity.

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