Top 10 JavaScript ES12 Features That Make Everyday Coding Easier

Why does JavaScript keep evolving?

JavaScript isn’t changing to keep up with trends; it’s changing to keep up with developers.

Every year, the ECMAScript (ES) specification incorporates lessons learned from real‑world usage: common mistakes, repeated patterns, and long‑standing pain points. The goal isn’t to reinvent the language, but to make everyday JavaScript feel more natural and less error‑prone.

What makes ES12 different?

ES12 introduces practical, small improvements to make code clearer and more efficient, with no flashy syntax changes.

If you’ve ever written extra checks to avoid runtime errors, duplicated logic to handle defaults, or struggled to keep code readable as it grows, ES12 addresses those exact problems.

Who should care about these features?

This guide is for developers who already uses JavaScript and want to:

• Write cleaner, more predictable code.
• Reduce bugs caused by edge cases.
• Adopt modern, stable features without added complexity.

Below, we’ll explore 10 JavaScript ES12 features and show how they make everyday development easier.

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1. Let & const

let creates variables that are only available inside the block where they are defined (like inside { … }). This helps avoid mistakes where variables accidentally affect code outside that block. You can change the value of a let variable later, but you cannot use it before you declare it; this is called the Temporal Dead Zone (TDZ).

Use let when the value changes, especially inside loops or if statements.

{
 // console.log(count); // Reference error due to TDZ
 let count = 0;
 count += 2;
 console.log(count);
}
// output: 2

const creates a variable you set once and cannot change later. This clearly tells anyone reading your code, “this value should stay the same.” But keep in mind, const only stops you from replacing the variable; it doesn’t freeze the contents. If you use const with an object or array, you can still update its properties or items, just not reassign the object itself.

Use const by default. Switch to let only when reassignment is necessary.

Code example (no reassignment)

const apiVersion = "v1";
// apiVersion = "v2"; // TypeError in strict mode / reassignment not allowed
console.log(apiVersion);
// output: v1

Code example (object rebinding)

const config = { debug: false };
config.debug = true; // Allowed: mutating object property
console.log(config.debug);
// config = {}; // Not allowed: rebinding the identifier
//output: true

2. Arrow function

Arrow functions help us write functions in a shorter way, and automatically use them from the code around them. They don’t have their own this, arguments, or prototype, and cannot be used as constructors.

Use them for callbacks, array operations, and methods that depend on the outer this. Use regular functions if you need your own this or arguments.

const nums = [1, 2, 3];
const doubled = nums.map(n => n * 2);
console.log(doubled);
// output: [2, 4, 6]

3. Destructuring

Destructuring lets you unpack values from arrays or properties from objects into individual variables in a single, clean statement. Instead of writing multiple lines to access values, you can extract them directly in a structured way.

const colors = ["red", "green", "blue"];

// Extract first two values
const [firstColor, secondColor] = colors;

console.log(firstColor);
console.log(secondColor);

// output:
red
green

4. Template literals

Template literals are one of the most useful modern JavaScript features. Instead of using regular quotes ‘ ‘ or ” “, we can use backticks `. This simple change makes strings more powerful and easier to work with.

With template literals, you can:

• Write text on multiple lines without using \n or concatenation.
• Insert variables directly inside the string using ${variable}.
• Embed expressions like calculations, conditions, or even function calls inside ${}.

  const name = "Alice";
  const age = 25;
  
  const message = `Hello, ${name}!
  Next year, you will be ${age + 1} years old.`;
  
  console.log(message);
  
  // Output
  Hello, Alice!
  Next year, you will be 26.

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5. Optional chaining

Optional chaining is an easier way to safely access nested properties in JavaScript without causing errors. Instead of manually checking every level, we can use ?. to stop the lookup if something is null or undefined, and the whole expression returns undefined.

With optional chaining, we can:

• Access deeply nested properties safely: obj?.a?.b?.c
• Safely read array items: arr?.[0]?.name
• Safely call functions only if they exist: fn?.()

  const user = {
    profile: { name: "Alice" },
    friends: [{ name: "Ravi" }],
    getGreeting: null
  };
  
  // Safely access nested properties, array items, and function calls
  const city = user.profile?.address?.city; // address is missing → undefined
  const firstFriend = user.friends?.[0]?.name; // "Ravi"
  const greeting = user.getGreeting?.(); // function is null → undefined (no error)
  
  console.log(city);
  console.log(firstFriend);
  console.log(greeting);
  
  // Output
  undefined
  Ravi
  undefined

6. Logical assignment operators

JavaScript already supports arithmetic and bitwise assignment operators. In ES12, it has extended support for logical assignment operators.

There are three new logical assignment operators:

• Logical Nullish Assignment (??=)
• Logical AND Assignment (&&=)
• Logical OR Assignment (||=)

Even though the syntax looks like an arithmetic assignment operator (+=), the logical assignment operators will not always perform the assignment. Instead, the assignment would happen only if the condition defined by the logical operator is met.

6.1 Logical nullish assignment

The logical nullish assignment operator (??=) will assign the value of the right operand to the left operand only if the left operand is null or undefined (nullish).

At first glance, the ??= operator might look a bit confusing because the expanded form of this operator is equivalent to x ?? (x = y).

const person = { name: 'John' };

person.name ??= 'User 1';
console.log(person.name); // output: John

person.age ??= 18;
console.log(person.age);  // output: 18

If we were to use an older ES version, the above code would look like the following:

const person = { name: 'John' };

if (person.name === undefined || person.name === null) {
  person.name = 'User 1';
}
console.log(person.name);

if (person.age === undefined || person.age === null) {
  person.age = 18;
}
console.log(person.age);

6.2 Logical AND assignment

The logical AND assignment operator (&&=) will perform the assignment if the left operand is truthy. Since we just covered the nullish assignment, usage of the logical AND assignment operator is pretty much self-explanatory.

const product = { stocks: 10 };

product.stocks &&= 20;
console.log(product.stocks); // output: 20

product.exp &&= '12/31/2021';
console.log(product.exp); // output: undefined

6.3 Logical OR assignment

The logical OR assignment operator (||=) is similar to the nullish assignment, but the left operand should be false for the assignment to occur. A value is considered false if it is null, undefined, false, 0, or NaN.

const product = {
  stocks: 0,
  exp: '12/31/2021'
};

product.stocks ||= 10;
console.log(product.stocks); // output: 10

product.exp ||= '01/31/2022';
console.log(product.exp); // output: 12/31/2021

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7. Private class fields

Private class fields in JavaScript let you create properties inside a class that cannot be accessed or modified from outside the class. This helps keep internal details hidden and prevents accidental changes, making your code more secure and maintainable.

To declare a private field, prefix its name with a # inside the class. These fields are only accessible within the class methods.

class User {
  #password; // private field

  constructor(name, password) {
    this.name = name;
    this.#password = password;
  }

  checkPassword(input) {
    return input === this.#password;
  }
}

const user = new User("Alice", "secret123");

console.log(user.name); // Alice
console.log(user.checkPassword("secret123")); // true
console.log(user.#password); // Error: Private field '#password' must be declared in an enclosing class

// Output
Alice
true
Error: Private field '#password' must be declared in an enclosing class

8. Iterator helpers

ES12 introduced iterator helpers such as map, filter, take, and drop, making working with iterators even easier. An iterator is like a tool that lets you go through a list of items one by one without having to load the entire list at once.

Before this, you had to convert iterators into arrays to transform them, which could use up a lot of memory for big lists or large data sets. With iterator helpers, you can process data step by step without creating additional arrays.

const users = [
  { name: 'Alice', age: 25, active: true },
  { name: 'Bob', age: 30, active: false },
  { name: 'Charlie', age: 35, active: true }
];

// Chain operations without creating intermediate arrays
const result = users.values()
  .filter(user => user.active)
  .map(user => user.name.toUpperCase())
  .take(2)
  .toArray();

console.log(result); // ['ALICE', 'CHARLIE']

9. New Set methods

Sets are great for storing unique values, and now they’re even better with built-in methods like union, intersection, and difference. These methods make combining and comparing sets easy without writing loops or extra logic.

const a = new Set([1, 2]);
const b = new Set([2, 3]);

console.log(a.union(b)); // Set {1, 2, 3}
console.log(a.intersection(b)); // Set {2}
console.log(a.difference(b)); // Set {1}

10. JSON module import

Working with JSON data requires extra steps like fetch or require, but now you can import JSON files directly as modules in modern JavaScript. This makes loading configuration or static data simple and efficient.

import config from './config.json' assert { type: 'json' };

console.log(config.apiUrl);

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Conclusion

Thanks for reading! JavaScript ES12 doesn’t ask you to relearn the language. It builds on what developers already do, refining common patterns and turning best practices into first‑class features.

By adopting these changes, you:

• Write clearer code with less effort.
• Avoid entire categories of runtime errors.
• Make your intent obvious to anyone reading your code.

Modern JavaScript isn’t about writing clever code! It’s about writing reliable, maintainable code that ages well. ES12 quietly helps you do exactly that.

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