Here are the key features introduced in ES13 (ECMAScript 2022), with detailed descriptions and examples:

1. Class Fields:

• Declare fields directly within class bodies:

JavaScript

class Person {
  name = "John Doe"; // Field declaration
  age = 30;

  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

2. Class Field Declarations:

• Initialize fields with default values during class definition:

JavaScript

class Person {
  name = ""; // Default value
  age = 0;
}

3. Private Fields:

• Encapsulation using the # symbol:

JavaScript

class Person {
  #name = "John"; // Private field

  getName() {
    return this.#name;
  }
}

4. Private Methods:

• Methods only accessible within the class:

JavaScript

class Person {
  #greet() {
    console.log("Hello, " + this.name);
  }
}

5. Ergonomic Brand Checks for Private Fields:

• Compiler-generated checks for accessing private fields:

JavaScript

class Person {
  #name = "John";

  greet(other) {
    if (other.#name === this.#name) { // Error: Cannot access private field
      console.log("We have the same name!");
    }
  }
}

6. Top-Level await:

• Use await outside of async functions:

JavaScript

async function fetchData() {
  const response = await fetch('https://api.example.com/data');
  // ...
}

fetchData(); // Now allowed at the top level

7. String.prototype.replaceAll():

• Replaces all occurrences of a substring within a string:

JavaScript

const text = "Hello, world!";
const newText = text.replaceAll("o", "a"); // "Halla, warld!"

8. Error Cause:

• Chain errors for better context:

JavaScript

throw new Error("File not found").cause(new Error("Network error"));

Remember: ES13 is relatively new, so browser support might vary. Check compatibility before using these features in production.