ecmastand.js

/**
 * ECMAScript Standards Overview
 * -----------------------------
 * ECMAScript (often abbreviated as ES) is the standardized specification for JavaScript
 * maintained by ECMA International in the ECMA-262 standard.
 * 
 * Major ECMAScript versions:
 * - ES1-3: Early versions (1997-1999)
 * - ES5: Released in 2009, added strict mode, JSON support, etc.
 * - ES6/ES2015: Major update with classes, arrow functions, promises, etc.
 * - ES2016-Present: Yearly release cycle with incremental updates
 */

// ES5 Features
"use strict"; // Strict mode (ES5)
var es5Array = [1, 2, 3, 4, 5];
es5Array.forEach(function(item) {
    console.log("ES5 forEach:", item);
});

// ES6/ES2015 Features
const es6Feature = () => {
    // Arrow functions
    const numbers = [1, 2, 3, 4, 5];
    
    // Array methods
    const doubled = numbers.map(n => n * 2);
    console.log("ES6 map:", doubled);
    
    // Template literals
    const name = "JavaScript";
    console.log(`ES6 template literals: Hello, ${name}!`);
    
    // Destructuring
    const person = { firstName: "John", lastName: "Doe", age: 30 };
    const { firstName, lastName } = person;
    console.log(`ES6 destructuring: ${firstName} ${lastName}`);
    
    // Classes
    class User {
        constructor(name) {
            this.name = name;
        }
        
        sayHello() {
            return `Hello, my name is ${this.name}`;
        }
    }
    
    const user = new User("Alice");
    console.log("ES6 classes:", user.sayHello());
    
    // Promises
    const simplePromise = new Promise((resolve) => {
        setTimeout(() => resolve("ES6 Promise resolved"), 100);
    });
    
    simplePromise.then(console.log);
};

// ES2017+ Features
const modernFeatures = async () => {
    // Async/await (ES2017)
    try {
        const result = await new Promise(resolve => 
            setTimeout(() => resolve("ES2017 async/await"), 100)
        );
        console.log(result);
        
        // Object rest/spread (ES2018)
        const obj1 = { a: 1, b: 2 };
        const obj2 = { ...obj1, c: 3 };
        console.log("ES2018 spread:", obj2);
        
        // Optional chaining (ES2020)
        const user = { 
            profile: { 
                address: null 
            } 
        };
        console.log("ES2020 optional chaining:", user?.profile?.address?.street);
        
        // Nullish coalescing (ES2020)
        const value = null;
        const defaultValue = value ?? "default";
        console.log("ES2020 nullish coalescing:", defaultValue);
    } catch (error) {
        console.error(error);
    }
};

// Execute examples
es6Feature();
modernFeatures();