1- Use const and let instead of var

Const declares a variable whose value cannot be changed. Let has block scope instead of function scope like var. Using const and let improves readability and avoid bugs.

const myName = "Mohammad";
myName = "Ali"; // Error, can't reassign const
let myAge = 30; 
if (true) {
 let myAge = 40; // Different variable
 console.log(myAge); // 40
}
console.log(myAge); // 30

2- Avoid global variables

Global variables can lead to namespace collisions and unintended side effects in large apps. Use local variables instead.

3- Use arrow functions

Arrow functions have a shorter syntax and lexically bind the this, arguments, super, and new. Target keywords.

// An Arrow function
const add = (a, b) => a + b;
// A function declaration
function add(a,b)=>{
 return a+b
};

4- Use spread operator

The spread operator expands an array into its individual elements. It is a concise way to combine arrays or objects.

const fruits = ["apple", "banana", "orange"];
const moreFruits = [...fruits, "mango"]; 
console.log(moreFruits) // ["apple", "banana", "orange", "mango"]

5- Use destructuring

Destructuring allows you to extract multiple values from arrays or properties from objects into distinct variables.

const [a, b] = [1, 2]; 
// a = 1, b = 2
const {name, age} = {name: "Omar", age: 30}; 
// name = "Omar", age = 30

6- Use template literals

Template literals use backticks () and ${} to embed expressions in a string.

const greeting = (name) => return `Hello, my name is ${name}!`;

7- Use default parameters

Default parameters allow named parameters to be initialized with default values if no value is passed.

const add = (a = 1, b = 2) => return a + b; 
add(10); // 12

8- Use object property shorthand

This shorthand allows you to initialize an object with variables.

const name = "Ahmed";
const age = 30;
const person = { name, age }; 
// {name: "Ahmed", age: 30}

9- Use promise and async/await

Promises and async/await make asynchronous code look synchronous and more readable.

10- Use JavaScript modules

Modules allow you to break up your code into separate files and reuse in other files or projects.