Must-Know 10 JavaScript Concepts Before Learning React

React is built on top of modern JavaScript (ES6+). If you jump straight into React without a solid understanding of these concepts, you might feel overwhelmed. Think of React as a toolbox — but if you don’t know how to use the basic tools (JavaScript features), building anything meaningful becomes frustrating.

In this article, we’ll go through essential JavaScript concepts that every aspiring React developer must know, along with simple examples you won’t forget.

🔑 Why ES6 and Beyond?

Before ES6 (ECMAScript 2015), JavaScript was clunky and verbose. ES6 introduced cleaner syntax, functional programming support, and features that React heavily relies on. Since React is functional by nature (hooks, components, state updates), mastering ES6+ is not optional — it’s the foundation.

1. Template Literals (Backticks)

Why? They make string handling easier, especially when you need interpolation or multi-line strings.

const name = "Amrit";
console.log(`Hello, ${name}! Welcome to React.`); 
// Hello, Amrit! Welcome to React.

✅ Useful in React when rendering dynamic values inside JSX:

2. Destructuring

Why? It helps extract values from arrays or objects cleanly. React props and state often need this.

const person = { name: "Amrit", age: 23 };
const { name, age } = person;
console.log(name, age); // Amrit 23

3. Rest & Spread Operators (...)

• Spread (...): Expands arrays/objects.

• Rest (...): Collects multiple elements into one.

const numbers = [1, 2, 3];
const newNumbers = [...numbers, 4, 5];
console.log(newNumbers); // [1, 2, 3, 4, 5]
function sum(...args) {
  return args.reduce((a, b) => a + b, 0);
}
console.log(sum(1,2,3)); // 6

4. Arrow Functions

Why? They are concise and automatically bind this. React functional components are essentially arrow functions.

const greet = (name) => `Hello, ${name}`;
console.log(greet("React"));

5. Ternary Operators

Why? Cleaner conditional rendering without if-else.

const isLoggedIn = true;
const message = isLoggedIn ? "Welcome back!" : "Please log in.";
console.log(message);

6. Nullish Coalescing (??)

Why? Provides a safe fallback only when the value is null or undefined (unlike || which also treats 0 or "" as false).

const userInput = null;
const value = userInput ?? "Default";
console.log(value); // "Default"

7. Optional Chaining (?.)

Why? Prevents errors when accessing nested properties that might not exist. Instead of crashing, it safely returns undefined.

const user = { profile: { name: "Amrit" } };
console.log(user.profile?.name); // Amrit
console.log(user.address?.street); // undefined (no error)

8. Short-Circuiting (&& and ||)

Why? Quick conditional checks without writing full if statements.

const name = "Amrit";
console.log(name && "Hello Amrit"); // Hello Amrit
console.log(null || "Default Value"); // Default Value

9. Promises

Why? To handle asynchronous code like API calls.

fetch("https://api.example.com/data")
  .then(res => res.json())
  .then(data => console.log(data))
  .catch(err => console.error(err));

In React, data fetching often uses Promises under the hood.

10. Async/Await

Why? Makes async code look synchronous and easier to read.

async function fetchData() {
  try {
    const res = await fetch("https://api.example.com/data");
    const data = await res.json();
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}
fetchData();

Final Thoughts

React is not a new language — it’s just JavaScript with extra power. If you’re comfortable with ES6+ concepts like template literals, destructuring, spread/rest, arrow functions, ternaries, short-circuiting, promises, and async/await, you’ll have a smooth journey into React.

Learning React without ES6 is like trying to build a house without knowing how to use a hammer. So Remember: Before mastering React Hooks, Context, or Redux, first master JavaScript ES6+. That’s the real foundation.