面试题复习

[xieyezi]

import "./styles.css";
import { useEffect } from "react";

// call 实现
// eslint-disable-next-line no-extend-native
Function.prototype.Mycall = function (context) {
  var context = context || window;
  context.fn = this;
  var args = [...arguments].slice(1);
  var result = context.fn(...args);
  delete context.fn;
  return result;
};

// apply 实现
// eslint-disable-next-line no-extend-native
Function.prototype.MyApply = function (context) {
  var context = context || window;
  context.fn = this;
  var args = [...arguments][1];
  var result = null;
  if (args) {
    result = context.fn(...args);
  } else {
    result = context.fn();
  }
  delete context.fn;
  return result;
};

// bind实现
// eslint-disable-next-line no-extend-native
Function.prototype.MyBind = function (context) {
  var self = this;
  let args = [...arguments].slice(1);
  return function () {
    let bindArgs = [...arguments].slice(0);
    let allArgs = args.concat(bindArgs);
    return self.apply(context, allArgs);
  };
};

// new 实现
function myNew() {
  let obj = {};
  let Cons = arguments[0];
  let args = [...arguments].slice(1);
  // console.log(Cons);
  // console.log(args);
  obj.__proto__ = Cons.prototype;
  let res = Cons.call(obj, ...args);
  return typeof res === "object" ? res : obj;
}

// 寻找数组中第k大的数
function findK(nums, k) {
  // 1.全排列，复杂度，O(nlogN)
  // nums = nums.sort((a, b) => b - a);
  // return nums[k - 1];
  // 2. 冒泡排序,复杂度，n*k
  for (let i = 0; i < k; i++) {
    for (let j = 0; j < nums.length - 1; j++) {
      if (nums[j] > nums[j + 1]) {
        [nums[j], nums[j + 1]] = [nums[j + 1], nums[j]];
      }
    }
  }
  return nums[nums.length - k];
}

//形式1：sum(1).sumof()
// 形式2：sum(1,2).sumof()
// 形式3：sum(1)(2, 3).sumof()
// 最终求得的结果，需要是各个出现的数字的和。

function sum(...lastArgs) {
  console.log("lastArgs", lastArgs);
  var callback = function (...args) {
    console.log("args", args);
    return sum(...[...lastArgs, ...args]);
  };
  callback.sumof = function () {
    return lastArgs.reduce((aggregated, number) => aggregated + number, 0);
  };
  return callback;
}


// 防抖实现 debunce
function debunce(fn,delay){
  let timer; 
  return function(...args) {
    if(timer) {
      clearTimeout(timer);
    }
    timer = setTimeout(() => {
      fn.apply(this,args)
    }, delay);
  }
}

// 节流实现
function throotle(fn,delay){
  let timer
  return function(...args) {
    if(!timer) {
      timer = setTimeout(()=>{
        timer = null
        fn.apply(this,args)
      },delay)
    }
  }
}

export default function App() {
  let foo = {
    value: 1
  };

  function bar(name, age) {
    console.log(name);
    console.log(age);
    console.log(this.value);
  }

  function Person(name, age) {
    this.name = name;
    this.age = age;
  }
  Person.prototype.sayName = function () {
    console.log(this.name + "hhh");
  };

  useEffect(() => {
    // bar.Mycall(foo, "xieyezi", 25);
    // bar.MyApply(foo, ["xieyezi", 25]);
    // let bindRes = bar.bind(foo, "xieyezi");
    // bindRes(19);
    // let a = myNew(Person, "xieyezi", 25);
    // console.log(a.sayName());
    // let k = findK([3, 2, 1, 5, 6, 4], 2);
    // console.log(k);
    let total = sum(1)(2, 3).sumof();
    console.log(total);
  }, []);

  return (
    <div className="App">
      <h1>Hello CodeSandbox</h1>
      <h2>Start editing to see some magic happen!</h2>
    </div>
  );
}