Gold nine silver ten factory front end by

drops

Implement a returnType

type MyReturnType<T> = T extends(... args)=> infer P ? P :never;
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Implement a custom react anti-shake hook

function useDebounce(fn, delay = 100) {
  const ref = useRef(fn);
  ref.current = function () {
    let timer;
    return function () {
      const context = this;
      const args = arguments;
      if (timer) {
        clearTimeout(timer);
        timer = null;
      }
      timer = seTimeout(fn.apply(context, args), delay)
    }
  }
  return ref.current;
}
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The maximum sum of paths in a binary tree

function findMaxPath(node) {
  let maxVal = -Infinity;
  function findMaxPath(node) {
    if(! node)return 0;
    const leftVal = Math.max(findMaxPath(node.left), 0);
    const rightVal = Math.max(findMaxPath(node.right), 0);
    const ps1 = node.val + Math.max(leftVal, rightVal);
    const ps2 = node.val + leftVal + rightVal;
    maxVal = Math.max(... [maxVal, ps1, ps2]);return ps1;
  }
  findMaxPath(node);
  return maxVal;
}
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To digital conversion

Write a function trans to convert the numbers into Chinese output, the input is not more than 1 trillion numbers.

For example: trans(123456) — one hundred and twenty three thousand four hundred and fifty-six

Trans (100010001) — 1010,001

let numChar = ['zero'.'一'.'二'.'三'.'four'.'five'.'六'.'seven'.'eight'.'九'];
let numUnit = [' '.'ten'.'best'.'千'];
let numSection = [' '.'万'.'亿'.'$'.'YiYi'];

// Map numbers to Chinese
function formatSection(num) {
  let arr = (num + ' ').split(' ').reverse();
  let str = ' ';
  for (let i = 0; i < arr.length; i++) {
    let char = arr[i] === 0 ? numChar[0] : numChar[arr[i]] + numUnit[i];
    str = char + str;
  }
  let s = str.replace(/ zero + / g.'zero').replace(+ $/ / to zero.' ');
  return s;
}

// Split the string by number
function formatNum(num, str) {
  let len = Math.ceil(str.length / num);
  let arr = [];
  let reverseStr = str.split(' ').reverse().join(' ');
  for (let i = 0; i < len; i++) {
    let result = reverseStr
      .slice(i * num, i * num + 4)
      .split(' ')
      .reverse()
      .join(' ');
    arr.unshift(result);
  }
  return arr;
}

function numberTranToCN(num) {
  let arr = formatNum(4, num + ' ');
  let list = [];
  for (let i = 0; i < arr.length; i++) {
    let str = formatSection(arr[i]);
    list.push(str);
  }
  let reverseList = list.reverse();
// add interval units
  for (let j = 0; j < reverseList.length; j++) {
    reverseList[j] += numSection[j];
  }
  return reverseList.reverse().join(' ');
}

console.log(numberTranToCN(12345));
console.log(numberTranToCN(1000003));
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Removes the least frequently occurring character from the string without changing the order of the original string

Example 1: “Ababac” — “ababa”

Example 2: “aaabbbcceeff” — “Aaabbb”

function task(str) {
  let min = Infinity;
  let map = new Map(a);for (let i = 0; i < str.length; i++) {
    const count = (map.get(str[i]) ?? 0) + 1;
    map.set(str[i], count);
  }

  min = Math.min(... map.values());return str.split(' ').reduce((pre, cur) = > {
    if (map.get(cur) === min) {
      return pre;
    } else {
      returnpre + cur; }},' ');
}
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Bytes to beat

Sword refers to Offer II 103. Minimum number of coins

79. Word search

affectionately

Hand write a usePrevious

function usePervious(newValue) {
  const pre = useRef();
  const cur = useRef();
  pre.current = cur.current;
  cur.current = newValue;
  return pre;
}
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Prototype chain

console.log(Function.__proto__ === Function.prototype);
//Function is a machine that makes machines
console.log(Object.__proto__ === Function.prototype);
console.log(Function.prototype.__proto__ === Object.prototype);
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Write a deep comparison

function compareObj(obj1, obj2) {
  if (typeofobj1 ! = ='object' && typeofobj2 ! = ='object') {
    return obj1 === obj2;
  }

  if (
    Array.isArray(obj1) &&
    Array.isArray(obj2) &&
    obj1.length === obj2.length
  ) {
    let result;
    for (let key in obj1) {
      result = compareObj(obj1[key], obj2[key]);
      if(! result) {return false; }}return true;
  }

  if (Object.keys(obj1).length === Object.keys(obj2).length) {
    if (Object.is(obj1, obj2)) return true;
    let result;
    let diff = true;
    Object.keys(obj1).forEach((key) = > {
      result = compareObj(obj1[key], obj2[key]);
      if(! result) { diff =false; }});return diff;
  }
  return false;
}

console.log(compareObj(1.1));
console.log(compareObj([1], [1]));
console.log(compareObj([1], [1.2]));
console.log(compareObj({ name: 123 }, { name: 123 }));
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Algorithm problem

All numbers in an array of length n+1 are in the range 1 to n, so at least one number in the array is repeated. Find any duplicate number in the array, but do not modify the input array. For example, if you input an array of length 8, “2,3,5,4,3,2,6,7”, the corresponding output would be duplicate numbers 2 or 3

function task(numbs) {
  for (let i = 0; i < numbs.length; i++) {
    const k = numbs[i];
    const j = numbs[k];
    if (k === j) {
      return k;
    } else{ [numbs[i], numbs[k]] = [numbs[k], numbs[i]]; }}}console.log(task([2.3.5.4.3.2.6.7]));
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Binary search

Given an ordered (non-descending) array A, which may contain repeating elements, minimize I such that A[I] is equal to target, and return -1 if it does not exist.

Array =,2,3,5,6,7,7,10 [1]

Target = 7, return 5

target = 8, return -1

function task(arr, target) {
  if(! arr || arr.length ===0) return -1;
  let left = 0,
    right = arr.length;
  while (left < right) {
    const mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      for (let i = mid; i > 0; i--) {
        if(arr[i] === target && arr? .[i -1] !== target) {
          returni; }}}else if (arr[mid] > target) {
      right = mid - 1;
    } else {
      left = mid + 1; }}return -1;
}

console.log(task([1.2.3.5.6.7.7.10].7));
console.log(task([1.2.3.5.6.7.7.10].8));
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Algorithm problem

347. The first K high frequency elements

var topKFrequent = function (nums, k) { 
    const map = new Map(a);for (let i = 0; i < nums.length; i++) { 
        map.set(nums[i], (map.get(nums[i]) ?? 0) + 1)}return Array.from(map).sort((a, b) = > b[1] - a[1]).slice(0, k).map(item= > item[0])};Copy the code

The ant gold dress

William chain calls macro task micro task

class PersonReal {
  constructor(name) {
    this.name = name;
    this.taskQueue = [];
    this.taskIsRunning = false;

    function task(name) {
      console.log(`Hi! This is ${name}! `);
    }
    this.taskQueue.push(task.bind(this, name));
    this._runQueue();
  }

  eat(food) {
    const task = (food) = > {
      console.log('Eat ' + food + '~');
    };
    this.taskQueue.push(task.bind(this, food));
    this._runQueue();
    return this;
  }

  sleep(time) {
    const task = new Promise((resolve, reject) = > {
      setTimeout(() = > {
        console.log(`Wake up after ${time}`);
        resolve();
      }, time * 1000);
    });
    this.taskQueue.push(task);
    this._runQueue();
    return this;
  }

  sleepFirst(time) {
    const task = new Promise((resolve, reject) = > {
      setTimeout(() = > {
        console.log(`Wake up after ${time}`);
        resolve();
      }, time * 1000);
    });
    this.taskQueue.unshift(task);
    this._runQueue();
    return this;
  }

  _runQueue() {
    if (this.taskIsRunning) return;
    this.taskIsRunning = true;

    const goNext = () = > {
      if (this.taskQueue.length) {
        let task = this.taskQueue.shift();
        if (task.then) {
          task.then(() = > {
            goNext();
          });
        } else{ task(); goNext(); }}else {
        this.taskIsRunning = false; }};Promise.resolve().then(() = >{ goNext(); }); }}function Person(name) {
  return new PersonReal(name);
}
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Netease Lingxi Business Division

Ts the topic

type DeepReadonly<T extends Record<string.any> > = {readonly [K in keyof T]: T[K] extends Record<string.any>? DeepReadonly<T[K]> : T[K]; };Copy the code

Extract and concatenate all strings under an Object that are not more than 50 characters long

/ / input:
const input = {
  a1: 'heading 1'.b2: 'title 2'.x3: {
    d: 'paragraph 1'.m: 12.k: true.c7: {
      s: 'abc'.k: [],},},};function getSummary(object) {
  let result = ' ';
  if (Object.keys(object).length === 0) return result;

  const task = (obj) = > {
    for (let key in obj) {
      if (typeof obj[key] === 'string') {
        const resultLen = result.length;
        const canAdd = resultLen + obj[key].length <= 50;
        if(canAdd) { result += obj[key]; }}else {
        task(obj[key])
      }
    }
  };

  task(object);
  return result;

}
console.log(getSummary(input));
/ / output:
// 'heading 1, heading 2, paragraph 1abc'
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To be continued