Real world use cases of object proxies

new Proxy(target, handler);

const prizeRegistry = {  karen: "First Prize - BMW X5",  mark: "Second Prize - Scooty",  athira: "Third Prize - Bicycle"};const prizeHandler = {  get(obj, prop) {    return prop in obj ?      obj[prop] :      "Consolation prize - Chocolate Bar";  }};const prizeList = new Proxy(prizeRegistry, prizeHandler);console.log(prizeList.karen);// expected output: "First Prize - BMW X5"console.log(prizeList.reena);// expected output: "Consolation prize - Chocolate Bar"

const validator = {  set(obj, prop, value) {    if (prop === 'weight') {      if (!Number.isInteger(value)) {        throw new TypeError('The weight is not an integer');      }      if (value > 200) {        throw new RangeError('The weight seems invalid');      }    }    // The default behavior to store the value    obj[prop] = value;    // Indicate success    return true;  }};const fish = new Proxy({}, validator);fish.weight = 100;console.log(fruit.weight); // expected output: 100fish.weight = 'small';    // Throws an exceptionfish.weight = 300;        // Throws an exception

const products = new Proxy([  { name: 'Firefox', type: 'browser' },  { name: 'SeaMonkey', type: 'browser' },  { name: 'Thunderbird', type: 'mailer' }],{  get(obj, prop) {    // The default behavior to return the value; prop is usually an integer    if (prop in obj) {      return obj[prop];    }    // Get the number of products; an alias of products.length    if (prop === 'number') {      return obj.length;    }    let result;    const types = {};    for (const product of obj) {      if (product.name === prop) {        result = product;      }      if (types[product.type]) {        types[product.type].push(product);      } else {        types[product.type] = [product];      }    }    // Get a product by name    if (result) {      return result;    }    // Get products by type    if (prop in types) {      return types[prop];    }    // Get product types    if (prop === 'types') {      return Object.keys(types);    }    return undefined;  }});console.log(products[0]);          // { name: 'Firefox', type: 'browser' }console.log(products['Firefox']);  // { name: 'Firefox', type: 'browser' }console.log(products['Chrome']);   // undefinedconsole.log(products.browser);     // [{ name: 'Firefox', type: 'browser' }, { name: 'SeaMonkey', type: 'browser' }]console.log(products.types);       // ['browser', 'mailer']console.log(products.number);      // 3