js面试题

题目juejin.cn/post/693789…

面试题

1.随机打乱

        function shuffle(arr) {
          arr.sort(() => Math.random() - 0.5);
          return arr;
        }
        console.log(shuffle(a));

2.反转

        let str = "I am a student!";
        function reserver(str) {
          console.log(str.split("").reverse().join(""));
        }
        reserver(str);

3.找交集

       function fun(arg) {
        let args = arguments;
        let result = [];
        let flag = false;
        [...args].map((item, index) => {
          minArr = item;
          if (item.length < minArr) {
            minArr = item;
          }
        });
        minArr.map((item, index) => {
          flag = [...args].every((ite) => ite.includes(item));
          flag && result.push(item);
        });
        console.log(result);
        return result;
      }
      fun([1, 2, 3], [2, 3, 4], [2, 3], [1, 3, 5]);

4.手写JSON.stringfy

      const stringOrOtherVal = (data) => {
        if (typeof data === "string") {
          return `"${data}"`;
        } else {
          return `${data}`;
        }
      };

      const myStringfy = (params)=> {
        let resultStr = "{";
        for (let key in params) {
          resultStr += `"${key}":${stringOrOtherVal(params[key])},`;
        }
        resultStr = resultStr.slice(0, resultStr.length - 1);
        resultStr += "}";
        console.log(resultStr);
        return resultStr;
      };

      let obj1 = { nane: "李明", age: 20 };
      let obj2 = { name: "李明", age: 20, 12: function () {} };
      myStringfy([1,2,3,4,8])

5.写一个节流函数

     let btn = document.getElementById("btn");
     
      function logs() {
        console.log(1);
      }
      
      btn.addEventListener("click", debounce(logs, 500), false);

      function resize(func, wait) {
        let timeout;
        return function () {
          if (!timeout) {
            timeout = setTimeout(() => {
              timeout = null;
              func.apply(this, arguments);
            }, wait);
          }
        };
      }

6.三次失败走reject

      let myAxios = function (option) {
        console.log("myAxios");
        return new Promise((resolve, reject) => {
          setTimeout(() => {
            reject("error");
          }, 1000);
        });
      };

      function runAxios(option, retry = 2) {
        let p = myAxios(option);
        if (retry > 0) {
          retry--;
          return new Promise((resolve, reject) => {
            p.then(resolve).catch(() => {
              resolve(runAxios(option, retry));
            });
          });
        }
        return p;
      }

      runAxios({
        url: "123/12",
      })
        .then(() => {
          console.log("success");
        })
        .catch((err) => {
          console.log("err");
        });

面试题总结

• 第1，2，3题还可以，第5题只有在addEventListener中才可以调用，在window.onresize=function(){},调用失败。第4，6完全不会，也不知道代码对不对。

笔试

字符串拼接

      function toString(map) {
        return Object.keys(map)
          .map((item, index) => {
            return (item = `${item}=${map[item]}`);
          })
          .join("&");
      }
      console.log(toString({ a: 1, b: 2, c: 3 }))

2.比较字符大小

      function sort(str) {
        return str
          .split("")
          .sort((a, b) => {
            return b.charCodeAt(0) - a.charCodeAt(0);
          })
          .join("");
      }
      console.log(sort("LeBronJames"));

3.正则替换

    function camel2snake(str) {
        return str.replace(/[A-Z]/g, (match) => `_${match.toLowerCase()}`);
      }
      console.log(camel2snake("fateStayNight"));

4.数组扁平化，递归

    function flattenDeep(list) {
        var flattenArr = [];
        for (var item of list) {
          if (typeof item == "number") {
            flattenArr.push(item);
          } else {
            flattenArr = flattenArr.concat(flattenDeep(item));
          }
        }
        return flattenArr;
      }

      function flattenDeep1(list) {
        return list.flat(Infinity);
      }

      console.log(flattenDeep([1, 2, [2, [3, [4], 5]]]));
      console.log(flattenDeep1([1, [2, [3, [4], 5]]]));

5.hash使用

     function count(list) {
        const map = new Map();
        for (var str of list) {
          if (map.has(str)) {
            map.set(str, map.get(str)+1);
          } else {
            map.set(str, 1);
          }
        }
        return Object.fromEntries(map);
      }
      console.log(count(["a", "a", "b", "c", "b", "a"]));

笔试总结

• 总体相对来说还行，第二题的charCodeAt和第三题 正则也是看了官方api才知道，还得多学多练。