在函数内部创建函数或常量Javascript

// 闭包示例：私有变量
function createCounter() {
    let count = 0;
    return {
        increment: function() {
            count++;
            console.log(count);
        },
        decrement: function() {
            count--;
            console.log(count);
        }
    };
}

const counter = createCounter();
counter.increment(); // 输出: 1
counter.increment(); // 输出: 2
counter.decrement(); // 输出: 1

// 高阶函数示例：装饰器
function withLogging(fn) {
    return function(...args) {
        console.log(`Calling function ${fn.name} with arguments:`, args);
        const result = fn(...args);
        console.log(`Function ${fn.name} returned:`, result);
        return result;
    };
}

function add(a, b) {
    return a + b;
}

const loggedAdd = withLogging(add);
console.log(loggedAdd(2, 3)); // 输出: Calling function add with arguments: [2, 3] 和 Function add returned: 5

// 确保在不需要时解除对闭包的引用
function createClosure() {
    let largeData = new Array(1000000).fill('some data');
    return function() {
        console.log(largeData[0]);
    };
}

const closure = createClosure();
// 使用完后手动解除引用
largeData = null;

// 使用函数缓存或记忆化
const memoizedAdd = (function() {
    const cache = {};
    return function(a, b) {
        const key = `${a},${b}`;
        if (cache[key] !== undefined) {
            return cache[key];
        }
        const result = a + b;
        cache[key] = result;
        return result;
    };
})();

console.log(memoizedAdd(2, 3)); // 输出: 5
console.log(memoizedAdd(2, 3)); // 直接从缓存中获取结果