Interview question on arrays

Question 1 : Given an array of object group them with same keys.

Question 1 : Given an array of object group them with same keys.

const data = [
  { category: "fruit", name: "apple" },
  { category: "vegetable", name: "carrot" },
  { category: "fruit", name: "banana" },
  { category: "vegetable", name: "broccoli" },
  { category: "fruit", name: "pear" },
];


Output:
{
  fruit: [
    { category: 'fruit', name: 'apple' },
    { category: 'fruit', name: 'banana' },
    { category: 'fruit', name: 'pear' }
  ],
  vegetable: [
    { category: 'vegetable', name: 'carrot' },
    { category: 'vegetable', name: 'broccoli' }
  ]
}

const groupBy = (array, key) => {
  return array.reduce((result, currentValue) => {
    const keyValue = currentValue[key];

    // If the key doesn't exist in the result object, create it and set it as an empty array
    if (!result[keyValue]) {
      result[keyValue] = [];
    }

    // Push the current object to the corresponding key array
    result[keyValue].push(currentValue);

    return result;
  }, {}); // Initialize the result object as an empty object
};

const groupedData = groupBy(data, "category");

Question 2 : Return the most repeating character from string

Question 2 : Return the most repeating character from string.

let s = "javascript";
output: a; // because a is most occurring

Solution 1

const mostRepeatingChar = (str) => {
  const charCount = {};

  // Count occurrences of each character
  for (const char of str) {
    if (charCount[char]) {
      charCount[char]++;
    } else {
      charCount[char] = 1;
    }
  }

  //   here charCount will become
  // { j:1, a:2,...}

  let maxCount = 0;
  let mostRepeating = "";

  // Find the character with the maximum count
  for (const char in charCount) {
    if (charCount[char] > maxCount) {
      maxCount = charCount[char];
      mostRepeating = char;
    }
  }

  return mostRepeating;
};

// Example usage
const inputString = "javascript";
const result = mostRepeatingChar(inputString);
console.log(result); // Output: "a"

Solution 2

    const mostRepeatingChar = (str) => {
      const charCount = str.split('').reduce((acc, char) => {
        acc[char] = (acc[char] || 0) + 1;
        return acc;
      }, {});

      return Object.keys(charCount).reduce((a, b) => charCount[a] > charCount[b] ? a : b);
    };

    // Example usage
    const inputString = "javascript";
    const result = mostRepeatingChar(inputString);
    console.log(result); // Output: "a"

Solution 3

const mostRepeatingChar = (str) => {
return str.split('').reduce((acc, char) => {
acc.count[char] = (acc.count[char] || 0) + 1;

if (acc.count[char] > acc.maxCount) {
  acc.maxCount = acc.count[char];
  acc.mostRepeating = char;
}

return acc;

}, { count: {}, maxCount: 0, mostRepeating: '' }).mostRepeating;
};

// Example usage
const inputString = "javascript";
const result = mostRepeatingChar(inputString);
console.log(result); // Output: "a"

Question 3 : Implement a function that flattens a nested array.

Question 3 : Implement a function that flattens a nested array.

function flattenArray(arr) {
    return arr.reduce((acc, curr) => 
      acc.concat(Array.isArray(curr) ? flattenArray(curr) : curr), 
    []);
}