秋招常考笔试题汇总

并发请求

出现情况：xhs一面

1. 实现一个批量请求函数 multiRequest(urls, maxNum)，要求如下：

   • 要求最大并发数 maxNum
   • 每当有一个请求返回，就留下一个空位，可以增加新的请求
   • 所有请求完成后，结果按照 urls 里面的顺序一次打印

async function multiRequest(urls, maxNum) {
  const results = [];
  let count = 0;
  while (count < urls.length) {
    const promises = [];
    for (let i = count; i < Math.min(count + maxNum, urls.length); i++) {
      promises.push(fetch(urls[i]).then(res => res.text()));
    }
    const responses = await Promise.allSettled(promises);
    for (let response of responses) {
      if (response.status === 'fulfilled') {
        results.push(response.value);
        count++;
      } else {
        console.error(response.reason);
      }
    }
  }
  console.log(results);
}


multiRequest(
  [
    'https://jsonplaceholder.typicode.com/posts/1',
    'https://jsonplaceholder.typicode.com/posts/2',
    'https://jsonplaceholder.typicode.com/posts/3',
    'https://jsonplaceholder.typicode.com/posts/4',
    'https://jsonplaceholder.typicode.com/posts/5',
    'https://jsonplaceholder.typicode.com/posts/6',
    'https://jsonplaceholder.typicode.com/posts/7',
    'https://jsonplaceholder.typicode.com/posts/8',
    'https://jsonplaceholder.typicode.com/posts/9',
    'https://jsonplaceholder.typicode.com/posts/10',
  ],
  3
);

实现lodash的get方法

字节二面

function get(object, path, defaultValue = 'undefined') 
{ //构造数组,将'['和']'替换成'.' 
    let newPath = []; 
    newPath = path.replace(/\[/g, '.').replace(/\]/g, '').split('.'); 
    return newPath.reduce((a, b) => { return (a || {})[b] }, object) || defaultValue 
}

红绿灯

dd二面

const generate =
  ({ color, delay }) =>
  () =>
    new Promise((resolve, reject) => {
      setTimeout(() => {
        resolve(color);
      }, delay);
    });

const lightConf = [
  { color: "red", delay: 3000 },
  { color: "green", delay: 2000 },
  { color: "yellow", delay: 1000 },
];


const promises = lightConf.map(generate);

const light  = async () => {
    while(true){
        for(const promise of promises){
            const color = await promise()
            console.log(color);
        }
    }
}

light()

flat函数

字节一面

const flat = (arr: any[], deep = Infinity) => {
  if(deep === 0) return arr
  return arr.reduce(
    (total, next) =>
      total.concat(Array.isArray(next) ? flat(next, deep - 1) : next),
    []
  );
};

promisify

字节一面

const promisify = (fn)=>function (...args) {
  return new Promise((resolve,reject)=>{
      args.push(function(err,data){
        if(err) reject(err)
        resolve(data)
      })
    fn(...args)
  })
}

子数组最大和

function maxSubArray(nums: number[]): number {
    let max = nums[0];
    let prev = nums[0];
    for (let i = 1;i<nums.length;i++){
       prev = Math.max(nums[i],prev+nums[i])
       max = Math.max(prev,max)
    }
    return max
};

深拷贝

const deepClone = <T  extends object >(obj: T, map = new WeakMap()): T => {
  if (obj === null || obj === undefined || typeof obj !== "object") return obj;
  if (map.has(obj)) return map.get(obj);
  const clonedObj = Array.isArray(obj)
    ? []
    : Object.create(Object.getPrototypeOf(obj));
  const keys = Reflect.ownKeys(obj);
  for (const key of keys) {
    if (obj[key] !== null && typeof obj[key] === "object") {
      clonedObj[key] = deepClone(obj[key], map);
    } else {
      clonedObj[key] = obj[key];
    }
  }
  return clonedObj;
};

科里化

const curryIt = (fn:Function):Function=>{
    const paramList:any[] = []
    function foo(...args){
        paramList.push(...args)
        if(paramList.length === fn.length){
            return fn(...paramList)
        }else {
            return foo
        }
    }
    return foo
}

快速排序

const quickSort = (arr,l,r)=>{
    if(l === r) return 
    let i = l-1,j=r+1
    const mid = arr[l+r >> 1]
    while(i<j){
        while(arr[++i]<mid) continue;
        while(arr[--j]>mid) continue;
        if(i<j) [arr[i],arr[j]] = [arr[j],arr[i]]
    }
    quickSort(arr,l,j)
    quickSort(arr,j+1,r)
}

const arr = [1,25,2,5,6,2,1]
quickSort(arr,0,arr.length-1)