js 命名空间冲突

var MyApp = MyApp || {};

MyApp.utils = {
    sayHello: function() {
        console.log("Hello from MyApp.utils");
    }
};

MyApp.utils.sayHello(); // 输出: Hello from MyApp.utils

var MyApp = (function() {
    var privateVar = "I'm private";

    function privateMethod() {
        console.log(privateVar);
    }

    return {
        publicMethod: function() {
            privateMethod();
        }
    };
})();

MyApp.publicMethod(); // 输出: I'm private

// utils.js
export function sayHello() {
    console.log("Hello from utils");
}

// main.js
import { sayHello } from './utils.js';

sayHello(); // 输出: Hello from utils

console.log(foo); // undefined
var foo = "bar";

console.log(foo); // ReferenceError: Cannot access 'foo' before initialization
let foo = "bar";