Comparison between ECMAScript ESand ECMAScript ES6)
1. Declaration of Variables
ES5:
- Use of var to declare variables. It has function as a scope and can give rise to hoisting.
var nombre = 'Maria';
ES6:
- Introduces let and const that have block as scope, improving security in the handling of variables.
let nombre = 'Maria'; // Variable que puede cambiar const edad = 30; // Constante, no puede cambiar
2. Arrow Functions
ES5:
- Traditional functions require more code and your handling of this can be confusing.
var suma = function(a, b) { return a + b; };
ES6:
- Arrow functions are more concise and do not change the context of this.
const suma = (a, b) => a + b;
3. Template Strings
ES5:
- String concatenation is done using the . operator
var saludo = 'Hola ' + nombre + ', tienes ' + edad + ' años.';
ES6:
- backticks (`) are used to create string templates, allowing interpolation.
const saludo = `Hola ${nombre}, tienes ${edad} años.`;
4. Default Parameters
ES5:
- There was no support for default parameters, so it was implemented manually.
function saludo(nombre) { nombre = nombre || 'Invitado'; return 'Hola ' + nombre; }
ES6:
- The default parameters are declared directly in the function signature.
function saludo(nombre = 'Invitado') { return `Hola ${nombre}`; }
5. Classes
ES5:
- The concept of classes did not exist. Builder functions and prototypes were used.
function Persona(nombre, edad) { this.nombre = nombre; this.edad = edad; } Persona.prototype.saludar = function() { return 'Hola, soy ' + this.nombre; };
ES6:
- The classes are introduced, a cleaner syntax closer to other programming languages.
class Persona { constructor(nombre, edad) { this.nombre = nombre; this.edad = edad; } saludar() { return `Hola, soy ${this.nombre}`; } }
6. Modules (Import and Export)
ES5:
- There was no native support for modules. Libraries such as RequireJS or CommonJS were used.
// CommonJS var modulo = require('modulo'); module.exports = modulo;
ES6:
- Introduces native support for modules with import and export.
// Exportar export const suma = (a, b) => a + b; // Importar import { suma } from './modulo';
7. Promises
ES5:
- There was no native promise handling. Callbacks were relied on to handle asynchrony, leading to problems like "Callback Hell".
function hacerAlgo(callback) { setTimeout(function() { callback('Hecho'); }, 1000); } hacerAlgo(function(resultado) { console.log(resultado); });
ES6:
- promises are introduced to handle asynchronous operations more cleanly.
const hacerAlgo = () => { return new Promise((resolve, reject) => { setTimeout(() => resolve('Hecho'), 1000); }); }; hacerAlgo().then(resultado => console.log(resultado));
8. Rest and Spread Operator
ES5:
- There was no support for easily combining or separating arrays or objects. Techniques such as the use of apply were used.
function sumar(a, b, c) { return a + b + c; } var numeros = [1, 2, 3]; sumar.apply(null, numeros);
ES6:
- The rest and spread operators are introduced for easier handling of argument lists and arrays.
// Spread const numeros = [1, 2, 3]; const resultado = sumar(...numeros); // Rest function sumar(...numeros) { return numeros.reduce((a, b) => a + b, 0); }
9. Destructuring
ES5:
- Extracting values from objects or arrays was manual and error-prone.
var persona = { nombre: 'Maria', edad: 30 }; var nombre = persona.nombre; var edad = persona.edad;
ES6:
- destructuring is introduced to extract values from objects and arrays in a cleaner way.
const { nombre, edad } = persona;
Conclusion
ECMAScript 6 (ES6) brings a large number of syntactic and functional improvements that simplify development in JavaScript, making it more readable, maintainable and efficient compared to ECMAScript 5 (ES5).
The above is the detailed content of Comparison between ECMAScript ESand ECMAScript ES6). For more information, please follow other related articles on the PHP Chinese website!

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