拼多多3.30前端笔试

两道选择，3道编程(Markdown编辑器，纯手撕，太难受了)

1.promise输出结果

const getPromise = ()=>{
      return new Promise((resolve,reject)=>{
        console.log('a new promise start')
        reject('error')
        console.log('a new promise end')
      })
    }
    async function run(){
      const promise = getPromise()
      promise.catch(console.log)
      const res = await promise
      console.log(res)
    }
    run()

2.代码执行结果

function modifyPerson(person){
      person.age = 2
      person = {age: 3}
      return person
    }
    const person = {age:1}
    modifyPerson(person)
    console.log(person)

3.找出字符串中连续出现最多的字符和对应的出现个数

const arr = str.match(/(.)\1+/g);
const maxLen = Math.max(...arr.map(s => s.length));
const result = arr.reduce((pre, curr) => {
	if (curr.length === maxLen) {
		pre[curr[0]] = curr.length
	}
	return pre;
}, {});
console.log(result) // {c: 3}

4.可指定超时时间的异步函数重试机制

function asyncFn() {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          if (Math.random() < 0.2) {
            console.log('inner success')
            resolve('success')
          } else {
            console.log('inner failed')
            reject('failed')
          }
        }, 5 * 1000 * Math.random())
      })
    }
    function runWithRetry(fn, retryTimes, timeout) {
      return new Promise((resolve, reject) => {
        const tryFn = () => {
          fn()
            .then((result) => {
              resolve(result);
            })
            .catch((error) => {
              if (retryTimes <= 0 || timeout <= 0) {
                reject(error);
              } else {
                console.log(`Retrying ${retryTimes} more times...`);
                setTimeout(() => {
                  tryFn();
                }, 5 * 1000 * Math.random());

                retryTimes--;
                timeout -= 5 * 1000 * Math.random();
              }
            });
        };

        tryFn();
      });
    }
    runWithRetry(asyncFn, 3, 10 * 1000).then(console.log, console.log)

5.补充css布局代码和Js代码，实现简易的九宫格抽奖功能(这波操作很拼多多