What are ES2023 - ES14 features?

1. Symbol.prototype.description is now writable

The description property of a Symbol object is now writable, meaning you can change it after the Symbol is created.

2. Array findLast and findLastIndex methods

These methods allow you to search arrays from the end, making it easier to locate items starting from the last element.

const arr = [1, 2, 3, 4, 5];

const lastEven = arr.findLast(num => num % 2 === 0);
console.log(lastEven); // 4

const lastEvenIndex = arr.findLastIndex(num => num % 2 === 0);
console.log(lastEvenIndex); // 3

3. Hashbang Grammar

JavaScript now supports the use of #! (hashbang) at the start of a script, enabling compatibility with Unix-like environments for direct script execution.

#!/usr/bin/env node
console.log("Hello, world!");

4. Change Array by Copy Methods

New methods such as toSpliced, with, toReversed, and toSorted allow for creating modified copies of arrays without mutating the original.

const arr = [1, 2, 3];

const newArr = arr.toReversed();
console.log(newArr); // [3, 2, 1]
console.log(arr);    // [1, 2, 3] (original array is unchanged)

const spliced = arr.toSpliced(1, 1, 9);
console.log(spliced); // [1, 9, 3]

5. Auto-accessor properties

A new syntax for declaring accessors (getters and setters) in classes, simplifying property definitions.

class Example {
    accessor value = 42;
}

const obj = new Example();
console.log(obj.value); // 42
obj.value = 100;
console.log(obj.value); // 100

6. RegExp v flag for Unicode sets

The v flag allows for more sophisticated matching of Unicode characters using Unicode property sets.

const regex = /\p{Emoji}/v;
console.log(regex.test("😊")); // true