ES6 vs Older JavaScript

JavaScript has evolved significantly over the years. ES6, also known as ECMAScript 2015, introduced many features that made JavaScript easier to write, read, and maintain. Before ES6, developers relied on older syntax and programming techniques to build interactive websites and web applications.

Understanding the differences between ES6 and older JavaScript helps beginners learn modern programming practices and understand why many developers prefer newer syntax.

What Is Older JavaScript?

Older JavaScript generally refers to JavaScript written using earlier ECMAScript standards, particularly ES5, which was released in 2009.

Before ES6, developers commonly used var for variable declarations, traditional functions for reusable code, and string concatenation to combine text with variables.

For example:

var name = "Alex";
var age = 22;

console.log("My name is " + name + " and I am " + age + " years old.");

Output:

My name is Alex and I am 22 years old.

This code works correctly, but combining several variables with strings can become difficult to read in larger applications.

What Is ES6 JavaScript?

ES6 stands for ECMAScript 2015. It introduced new language features, including let, const, arrow functions, template literals, destructuring, classes, modules, and promises.

These features help developers write cleaner and more maintainable code.

For example, the previous code can be rewritten using ES6 syntax:

const name = "Alex";
const age = 22;

console.log(`My name is ${name} and I am ${age} years old.`);

Output:

My name is Alex and I am 22 years old.

The template literal makes it easier to combine text and variables.

Key Differences Between ES6 and Older JavaScript

Feature	Older JavaScript (ES5)	ES6 JavaScript
Variable declarations	Commonly uses `var`	Introduces `let` and `const`
Function syntax	Traditional functions	Adds arrow functions
String formatting	String concatenation	Template literals
Default parameters	Usually handled manually	Supports default parameters
Array and object values	Often extracted manually	Supports destructuring
Copying and combining values	Often uses methods such as `concat()` or `apply()`	Adds spread syntax
Function arguments	Often handled through `arguments`	Supports rest parameters
Object-oriented syntax	Constructor functions and prototypes	Adds class syntax
Code organization	Often uses scripts and patterns such as the module pattern	Adds standard `import` and `export` modules
Asynchronous operations	Callbacks were commonly used	Adds native promises

ES6 did not remove older JavaScript syntax. Much of the older syntax remains valid in modern JavaScript.

Variable Declarations: var vs let and const

In older JavaScript, developers commonly used var to declare variables. ES6 introduced let and const to provide block-scoped declarations.

Older JavaScript:

var score = 50;
score = 80;

console.log(score);

ES6 JavaScript:

let score = 50;
score = 80;

const country = "India";

console.log(score);
console.log(country);

Output:

80
India

Use let when a variable needs reassignment and const when its binding should not be reassigned. Both are block-scoped, unlike var, which is function-scoped.

Function Syntax: Traditional Functions vs Arrow Functions

Older JavaScript commonly uses traditional function expressions.

var multiply = function(a, b) {
    return a * b;
};

console.log(multiply(4, 5));

With ES6, you can use an arrow function.

const multiply = (a, b) => a * b;

console.log(multiply(4, 5));

Output:

Arrow functions provide shorter syntax. However, they do not have their own this binding, so they are not a direct replacement for every traditional function.

String Formatting: Concatenation vs Template Literals

Older JavaScript often combines strings using the + operator.

var name = "Sarah";

console.log("Welcome, " + name + "!");

ES6 provides template literals using backticks.

const name = "Sarah";

console.log(`Welcome, ${name}!`);

Output:

Welcome, Sarah!

Template literals also make multiline strings and embedded expressions easier to write.

Object Creation: Constructor Functions vs Classes

Before ES6, developers commonly used constructor functions to create objects with shared properties and methods.

function Person(name) {
    this.name = name;
}

Person.prototype.greet = function() {
    console.log("Hello, " + this.name);
};

var person = new Person("Alex");

person.greet();

ES6 introduced class syntax, which provides a more familiar way to define constructors and methods.

class Person {
    constructor(name) {
        this.name = name;
    }

    greet() {
        console.log(`Hello, ${this.name}`);
    }
}

const person = new Person("Alex");

person.greet();

Output:

Hello, Alex

JavaScript classes use prototype-based inheritance behind the scenes. They provide a clearer syntax for many object-oriented programming tasks.

Which Is Better: ES6 or Older JavaScript?

For most new projects, modern JavaScript syntax is a good choice because it offers convenient features and improves code readability.

However, older JavaScript remains important for understanding legacy projects, maintaining existing applications, and learning how the language has evolved.

The best approach is to understand the fundamentals first and then learn modern syntax for the same concepts.

Frequently Asked Questions

Is ES6 different from JavaScript?

ES6 is an edition of the ECMAScript language standard that defines JavaScript features. It introduced many additions to the language in 2015.

Is older JavaScript still used?

Yes. Existing websites and applications may contain older syntax. Developers often need to read and maintain this code.

Should beginners learn ES5 or ES6 first?

Beginners can start with modern JavaScript while learning the fundamentals. Understanding older syntax is also helpful when reading legacy code.

Does ES6 make JavaScript faster?

ES6 primarily introduced language features and improvements to developer productivity. Performance depends on the code, runtime, and implementation rather than simply whether ES6 syntax is used.

Is ES6 still relevant today?

Yes. ES6 features remain widely used in modern JavaScript development, although the language has continued to evolve with newer ECMAScript editions.

What to Learn Next

Continue learning the following JavaScript topics: