JS 函数元编程技巧 - 操作函数自身属性与行为的高级使用方法

call

apply

bind

this

function greet(name) {
    console.log(`Hello, ${name}! I am ${this.id || 'anonymous'}.`);
}

const user = { id: 'Alice' };
greet.call(user, 'Bob'); // Hello, Bob! I am Alice.

const boundGreet = greet.bind({ id: 'Charlie' });
boundGreet('David'); // Hello, David! I am Charlie.

function calculate(a, b) {
    // ...复杂的计算
    return a + b;
}
calculate.description = '一个简单的加法函数';
calculate.version = '1.0.0';

console.log(calculate.description); // 访问函数的元数据

Object.defineProperty

function myUtility() { /* ... */ }
Object.defineProperty(myUtility, 'secretKey', {
    value: 'super_secret_value',
    writable: false,    // 不可修改
    enumerable: false,  // 不可枚举
    configurable: false // 不可删除或重新定义
});

// 尝试修改会失败（在严格模式下报错）
// myUtility.secretKey = 'new_value';

processOrder(order)

processOrder

processOrder

// 权限校验装饰器
function withAuth(fn) {
    return function(...args) {
        // 假设第一个参数是需要权限的资源
        if (!checkPermissions(args[0])) {
            console.error('权限不足！');
            return;
        }
        return fn.apply(this, args);
    };
}

// 模拟权限检查
function checkPermissions(order) {
    return order && order.userId === 'admin'; // 简单示例
}

// 日志记录装饰器
function withLogging(fn) {
    return function(...args) {
        console.log(`Calling ${fn.name} with args:`, args);
        const result = fn.apply(this, args);
        console.log(`${fn.name} returned:`, result);
        return result;
    };
}

// 原始业务函数
function processOrder(order) {
    console.log(`Processing order: ${order.id} by user: ${order.userId}`);
    // ... 实际的订单处理逻辑
    return { status: 'success', orderId: order.id, userId: order.userId };
}

// 组合装饰器
const secureLoggedProcessOrder = withLogging(withAuth(processOrder));

console.log('--- 尝试处理管理员订单 ---');
secureLoggedProcessOrder({ id: '123', userId: 'admin' });

console.log('\n--- 尝试处理普通用户订单 ---');
secureLoggedProcessOrder({ id: '456', userId: 'guest' });

processOrder

function memoize(fn) {
    const cache = {};
    return function(...args) {
        const key = JSON.stringify(args); // 简单的缓存键生成
        if (cache[key]) {
            console.log('从缓存中获取结果');
            return cache[key];
        }
        const result = fn.apply(this, args);
        cache[key] = result;
        return result;
    };
}

function expensiveCalculation(num) {
    console.log('执行昂贵计算...');
    let sum = 0;
    for (let i = 0; i < num * 1000000; i++) {
        sum +=