JavaScript ES6

ES6, also known as ECMAScript 2015, introduced several new features and syntax improvements to JavaScript. Here are some key aspects of ES6:

let and const

  • let allows you to declare block-scoped variables, which are only accessible within the nearest set of curly braces {}. This helps prevent accidental variable reassignment and provides better scoping.
  • const is used to declare block-scoped constants whose values cannot be reassigned. However, properties of objects declared with const can still be modified.

Arrow Functions

  • Arrow functions (=>) provide a more concise syntax for writing function expressions.
  • They lexically bind the this value, eliminating issues with this binding in regular functions.


  • ES6 introduced a new syntax for creating classes, making object-oriented programming in JavaScript more straightforward.
  • Classes support inheritance, constructors, static methods, and other features found in traditional object-oriented languages.


  • ES6 provides a standardized module system for organizing and sharing code across files.
  • Modules can import and export functions, objects, and other values, promoting code reusability and maintainability.

Template Literals

  • Template literals (enclosed in backticks ` “) allow for string interpolation and multiline strings, making it easier to work with strings.


  • Destructuring allows you to extract values from arrays or properties from objects and assign them to distinct variables.
  • This makes working with complex data structures more concise and readable.

Spread Operator

  • The spread operator (...) allows you to spread elements of an array or properties of an object into another array or object.
  • It simplifies operations like array concatenation, object cloning, and function argument passing.

Default Parameters

  • ES6 introduced default parameter values for functions, allowing you to provide fallback values if arguments are not supplied.

Rest Parameters

  • The rest parameter syntax (...) allows you to represent an indefinite number of arguments as an array within a function.

Promises and async/await

  • Promises provide a more structured way of handling asynchronous operations in JavaScript.
  • The async/await syntax makes working with Promises more intuitive and readable.

These are just some of the major features introduced in ES6. The update aimed to make JavaScript more modern, expressive, and aligned with programming paradigms found in other languages, while maintaining backward compatibility.

Tips & Tricks

Var, Let, Const

In ES6 (ECMAScript 2015), let and const were introduced as new ways to declare variables, offering improvements over the traditional var declaration. Here’s a summary of the differences and use cases:

varVariables declared with var have function scope or global scope if declared outside a function.
They can be re-declared and updated within their scope.
They are hoisted to the top of their scope and initialized with undefined.
letVariables declared with let have block scope (within { }), which helps prevent accidental overwriting.
They cannot be re-declared within the same scope.
They are hoisted to the top of their block, but not initialized. Trying to use a let variable before declaration will cause a ReferenceError.
Recommended for most variable declarations in modern JavaScript.
constVariables declared with const have block scope, similar to let.
They cannot be re-declared or re-assigned within the same scope.
They must be assigned an initial value during declaration.
While the variable reference cannot be reassigned, the properties of objects declared with const can be modified.
Recommended for declaring variables whose values should not change, such as constants or configuration values.


Working with objects: how to define an object with one property (name) and one method (walk)

const person = {
  name: 'Jack',
  walk(): {}

How to call the method

// option 1
// option 2
// option 3
const tagetMember = 'walk';

If you know ahead of time what property or method you’re going to access, then use the dot notation (first option). Otherwise, use the last two options.

The this keyword