muhsalaa

// question at https://muhsalaa.com/journal/3ab005b6-2c66-4ccc-b7bb-df1be5ff8777

function highlight(nominal, uniqueCode) {
  // convert number to string
  const totalString = String(nominal + uniqueCode);
  const nominalString = String(nominal);
  let count = 0;
  
  // loop to count similar character by comparing nominal and total (nominal+unique code)
  for (let x = 0; x < totalString.length; x++) {

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function useTraceUpdate(props) {
  const prev = React.useRef(props);
  React.useEffect(() => {
    const changedProps = Object.entries(props).reduce((ps, [k, v]) => {
      if (prev.current[k] !== v) {
        ps[k] = [prev.current[k], v];
      }
      return ps;
    }, {});
    if (Object.keys(changedProps).length > 0) {

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import React, { useState, useCallback, useRef, useEffect } from 'react';

export default function Multipleform() {
  let [data, setData] = useState([...Array(5000).fill('')]);

  // wrap handler with useCallback to keep its reference
  // so React.memo will not consider it change overtime
  const handler = useCallback((value = '', i = 0) => {
    setData((state) => {
      // return state modified with map to change value of certain index

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// 1. https://www.hackerrank.com/challenges/counting-valleys/problem
// count how many valleys has been passed by hiker

function countingValleys(n, s) {
  let valleys = 0;
  let count = 0;
  s.split('').forEach(x => {
  	if (x === 'U') {
      count += 1 
      // check if count === 0 means it is the time when hiker go to sea level from valleys, valleys += 1

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// input: ['tea','you', 'eat', 'ate', 'ouy', 'hard']
// output: [
//     ['tea', 'eat', 'ate'],
//     ['you', 'ouy'],
//     ['hard']
// ]

function groupAnagram(arr) {
  // we will put result here
  const output = {};

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/**
 * Convert a url of image to base64 string
 * @param {string} imgUrl string of image url            
 */

function convertBase64(imgUrl) {
  return new Promise((resolve) => {
    var img = new Image();
    // onload fires when the image is fully loadded, and has width and height
    img.onload = () => {

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function joinArrayRange(array, start, end, color, normalize) {
  let result = '';
  const joined = array.slice(start, end + 1).join(' ');
  array.splice(start, end - start + 1, `<span style="background: ${color}">${joined}</span>`, ...[...Array(end - start).fill('<xxx>')]);
  if (normalize) {
    result = array.filter(item => item !== '<xxx>').join(' ');
  } else {
    result = array.join(' ');
  }