How to Write Clean and Efficient ECMAScript Code

Are you tired of writing bloated, messy code in ECMAScript (also known as JavaScript or TypeScript)? Do you want to write code that is clean, efficient, and easy to read and maintain? Then you're in the right place! In this article, we'll cover some tips and best practices for writing clean and efficient ECMAScript code that will make your codebase sparkle.

Use Let and Const Instead of Var

One of the biggest mistakes new developers make when writing ECMAScript code is to use the var keyword instead of let or const. var has some issues, such as variable hoisting, that can lead to bugs and make your code harder to reason about. let and const, on the other hand, are block-scoped and have more predictable behavior. Use let when you need to reassign a variable, and const when you don't.

// bad
var a = 1;
// good
let b = 2;
const c = 3;

Use Arrow Functions

Arrow functions were introduced in ECMAScript 6 and are a shorthand way of writing functions. They not only make your code more concise, but also provide lexical scoping, meaning that this is bound to the parent scope, instead of the function itself. This makes it easier to reason about this in your code.

// bad
function add(a, b) {
  return a + b;

// good
const add = (a, b) => a + b;

Use Template Literals

Template literals are another feature introduced in ECMAScript 6 that make it easier to write strings. They allow you to embed expressions inside a string, and also provide multiline strings. This makes it easier to write complex strings and reduces the need for string concatenation.

// bad
const name = "John";
const message = "Hello, " + name + "!";

// good
const name = "John";
const message = `Hello,

Destructure Arrays and Objects

Destructuring allows you to extract values from arrays and objects into variables. This not only makes your code more concise, but also makes it more readable, as it clarifies what the values represent.

// bad
const arr = [1, 2, 3];
const a = arr[0];
const b = arr[1];
const c = arr[2];

// good
const arr = [1, 2, 3];
const [a, b, c] = arr;

// bad
const obj = { name: "John", age: 30 };
const name =;
const age = obj.age;

// good
const obj = { name: "John", age: 30 };
const { name, age } = obj;

Use Default Parameters

Default parameters allow you to provide a default value for a function parameter, in case the parameter is not passed in or is undefined. This can help reduce the amount of boilerplate code you need to write, as well as make your code more readable.

// bad
function greet(name) {
  if (name === undefined) {
    name = "Stranger";
  console.log(`Hello, ${name}!`);

// good
function greet(name = "Stranger") {
  console.log(`Hello, ${name}!`);

Use Rest and Spread Operators

The rest and spread operators allow you to work with arrays and objects in a more flexible way. The rest operator allows you to gather remaining arguments into an array, while the spread operator allows you to spread an array or object into separate arguments.

// rest operator
function multiply(multiplier, ...nums) {
  return => num * multiplier);

console.log(multiply(2, 1, 2, 3)); // [2, 4, 6]

// spread operator
const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const arr3 = [...arr1, ...arr2];

console.log(arr3); // [1, 2, 3, 4, 5, 6]

Use Functional Programming Techniques

Functional programming is a paradigm that emphasizes writing code that is declarative and composable. It makes use of higher-order functions, immutability, and pure functions to make code easier to reason about and maintain. Some examples of functional programming techniques in ECMAScript include map, filter, and reduce.

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

// map
const doubled = => num * 2);

console.log(doubled); // [2, 4, 6, 8, 10]

// filter
const even = arr.filter(num => num % 2 === 0);

console.log(even); // [2, 4]

// reduce
const sum = arr.reduce((acc, num) => acc + num, 0);

console.log(sum); // 15

Use Immutable Data Structures

Immutable data structures are data structures that cannot be modified once they are created. This can help reduce bugs and make your code more predictable, as well as make it easier to reason about. Some examples of immutable data structures in ECMAScript include Object.assign, concat, and Object.freeze.

// Object.assign
const obj1 = { name: "John" };
const obj2 = { age: 30 };
const obj3 = Object.assign({}, obj1, obj2);

console.log(obj3); // { name: "John", age: 30 }

// concat
const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const arr3 = arr1.concat(arr2);

console.log(arr3); // [1, 2, 3, 4, 5, 6]

// Object.freeze
const obj = Object.freeze({ name: "John", age: 30 });
obj.age = 40; // error: can't modify frozen object

Use Promises and Async/Await

Promises and async/await are techniques used for handling asynchronous code in ECMAScript. Promises allow you to write code that can handle success and error cases, without having to resort to complex nested callbacks. Async/await builds on top of Promises, and allows you to write asynchronous code in a more synchronous way, making it easier to reason about and maintain.

// Promises
function fetchData() {
  return fetch("")
    .then(response => response.json())
    .then(data => {
    .catch(error => {

// Async/await
async function fetchData() {
  try {
    const response = await fetch("");
    const data = await response.json();
  } catch (error) {

Use Linters and Formatters

Linters and formatters are tools that can help you write clean and consistent ECMAScript code. Linters provide warnings or errors for code that doesn't follow best practices or code quality standards, while formatters automatically format your code to a consistent style. Some popular linters for ECMAScript include ESLint and JSLint, while popular formatters include Prettier and StandardJS.


Writing clean and efficient ECMAScript code can be a challenging task, but by following the tips and best practices outlined in this article, you can make your codebase sparkle. Remember to use let and const instead of var, use arrow functions, template literals, and destructuring to write more concise code, use default parameters and functional programming techniques to make your code more readable and maintainable, and use promises and async/await to handle asynchronous code. By using these techniques, you'll be able to write code that is easier to reason about, easier to maintain, and more fun to work with.

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