//閉包實(shí)例代碼
function fn1() {
  let a = 1;
  function fn2() {
    a++;
    console.log(a);
  }
  return fn2;
}
const fn2 = fn1();
//閉包函數(shù)執(zhí)行完后外部作用域變量仍然存在，并保持狀態(tài)
fn2() //2
fn2() //3

let say = (function(){
  let val = 'hello world';
  function say(){
    console.log(val);
  }
  return say;
})()

// 節(jié)流函數(shù)封裝
function throttle(func, delay) {
  let timer = null;
  return function () {
    if (!timer) {
      timer = setTimeout(() => {
        func.apply(this, arguments);
        timer = null;
      }, delay);
    }
  };
}
// 防抖函數(shù)封裝
function debounce(func, delay) {
  let timer = null;
  return function () {
    clearTimeout(timer);
    timer = setTimeout(() => {
      func.apply(this, arguments);
    }, delay);
  };
}

//柯里化前
function add(a, b, c) {
  return a + b + c;
}
console.log(add(1, 2, 3)); //6
//柯里化后
function addCurried1(a) {
  return function (b) {
    return function (c) {
      return a + b + c;
    };
  };
}
//箭頭函數(shù)簡(jiǎn)寫
const addCurried2 = (a) => (b) => (c) => a + b + c;
console.log(addCurried1(1)(2)(3)); //6
console.log(addCurried2(1)(2)(3)); //6

function calculator() {
  let result = 0;
  function add(num) {
    result += num;
    return this;
  }
  function subtract(num) {
    result -= num;
    return this;
  }
  function multiply(num) {
    result *= num;
    return this;
  }
  function divide(num) {
    result /= num;
    return this;
  }
  function getResult() {
    return result;
  }
  function clear() {
    result = 0;
    return this;
  }
  return {
    add,
    subtract,
    multiply,
    divide,
    getResult,
    clear,
  };
}
const calc = calculator();
const result = calc.add(5).subtract(2).divide(3).multiply(6).getResult();
console.log(result); // 輸出：6

function createIterator(arr) {
  let index = 0;
  return {
    next: function() {
      if (index < arr.length) {
        return {
          value: arr[index++],
          done: false
        };
      } else {
        return {
          done: true
        };
      }
    }
  };
}
const myIterator = createIterator([1, 2, 3]);
console.log(myIterator.next()); // { value: 1, done: false }
console.log(myIterator.next()); // { value: 2, done: false }
console.log(myIterator.next()); // { value: 3, done: false }
console.log(myIterator.next()); // { done: true }

function createPubSub() {
  // 存儲(chǔ)事件及其對(duì)應(yīng)的訂閱者
  const subscribers = {};
  // 訂閱事件
  function subscribe(event, callback) {
    // 如果事件不存在，則創(chuàng)建一個(gè)新的空數(shù)組
    if (!subscribers[event]) {
      subscribers[event] = [];
    }
    // 將回調(diào)函數(shù)添加到訂閱者數(shù)組中
    subscribers[event].push(callback);
  }
  // 發(fā)布事件
  function publish(event, data) {
    // 如果事件不存在，則直接返回
    if (!subscribers[event]) {
      return;
    }
    // 遍歷訂閱者數(shù)組，調(diào)用每個(gè)訂閱者的回調(diào)函數(shù)
    subscribers[event].forEach((callback) => {
      callback(data);
    });
  }
  // 返回訂閱和發(fā)布函數(shù)
  return {
    subscribe,
    publish,
  };
}
// 使用示例
const pubSub = createPubSub();
// 訂閱事件
pubSub.subscribe("event1", (data) => {
  console.log("訂閱者1收到事件1的數(shù)據(jù):", data);
});
pubSub.subscribe("event2", (data) => {
  console.log("訂閱者2收到事件2的數(shù)據(jù):", data);
});
// 發(fā)布事件
pubSub.publish("event1", "Hello");
// 輸出: 訂閱者1收到事件1的數(shù)據(jù): Hello
pubSub.publish("event2", "World");
// 輸出: 訂閱者2收到事件2的數(shù)據(jù): World

function createClosure() {
  let value = 'Hello';
  // 閉包函數(shù)
  var closure = function() {
    console.log(value);
  };
  // 解綁定閉包函數(shù)，并釋放資源
  var releaseClosure = function() {
    value = null; // 解除外部變量的引用
    closure = null; // 解除閉包函數(shù)的引用
    releaseClosure = null; // 解除解綁函數(shù)的引用
  };
  // 返回閉包函數(shù)和解綁函數(shù)
  return {
    closure,
    releaseClosure
  };
}
// 創(chuàng)建閉包
var closureObj = createClosure();
// 調(diào)用閉包函數(shù)
closureObj.closure(); // 輸出：Hello
// 解綁閉包并釋放資源
closureObj.releaseClosure();
// 嘗試調(diào)用閉包函數(shù)，此時(shí)已解綁，不再引用外部變量
closureObj.closure(); // 輸出：null