The most common elementary algorithms in JavaScript

arrayAlgos.js

// The most common elementary algorithms in JavaScript 
'use strict';

const testNumbers = [8, 6, 3, 7, 3, 8, 4, 4, 9, 1, 2, 8];

// 1. Search

function contains(array, elemToFind) {
  for (let i = 0; i < array.length; i++) {
    if (array[i] === elemToFind) {
      return true;
    }
  }

  return false;
}

console.log(contains(testNumbers, 4));

// 2. Search for any one of multiple elements

function containsAnyOf(array, elemsToFind) {
  for (let i = 0; i < array.length; i++) {
    for (let j = 0; j < elemsToFind.length; j++) {
      if (array[i] === elemsToFind[j]) {
        return true;
      }
    }
  }

  return false;
}

console.log(containsAnyOf(testNumbers, [3, 5]));

// 3. Counting

function count(array, elemToCount) {
  let count = 0;

  for (let i = 0; i < array.length; i++) {
    if (array[i] === elemToCount) {
      count = count + 1;
    }
  }

  return count;
}

console.log(count(testNumbers, 3));

// 4. Filtering

function filter(array, elemToFind) {
  let filteredArray = [];

  for (let i = 0; i < array.length; i++) {
    if (array[i] === elemToFind) {
      filteredArray.push(array[i]);
    }
  }

  return filteredArray;
}

console.log(filter(testNumbers, 4));

// 5. Summing

function sum(numbers) {
  let sum = 0;

  for (let i = 0; i < numbers.length; i++) {
    sum = sum + numbers[i];
  }

  return sum;
}

console.log(sum(testNumbers));

// 6. Finding the minimum value

function min(numbers) {
  let minNumber = numbers[0];

  for (let i = 1; i < numbers.length; i++) {
    if (numbers[i] < minNumber) {
      minNumber = numbers[i];
    }
  }

  return minNumber;
}

console.log(min(testNumbers));

// 7. Finding the maximum value

function max(numbers) {
  let maxNumber = numbers[0];

  for (let i = 1; i < numbers.length; i++) {
    if (numbers[i] > maxNumber) {
      maxNumber = numbers[i];
    }
  }

  return maxNumber;
}

console.log(max(testNumbers));

// 8. Calculating the number of occurrences

function getFrequencies(array) {
  let frequencies = {};

  for (let i = 0; i < array.length; i++) {
    let currentElem = array[i];

    if (frequencies[currentElem] === undefined) {
      frequencies[currentElem] = 0;
    }

    frequencies[currentElem] = frequencies[currentElem] + 1;
  }

  return frequencies;
}

console.log(getFrequencies(testNumbers));

// 9. Finding the element with the highest occurrence

function getMostFrequentElement(array) {
  let frequencies = getFrequencies(array);
  let keys = Object.keys(frequencies);

  let maxKey = keys[0];
  let maxCount = frequencies[maxKey];

  for (let i = 1; i < keys.length; i++) {
    let currentKey = keys[i];
    let currentCount = frequencies[currentKey];

    if (currentCount > maxCount) {
      maxCount = currentCount;
      maxKey = currentKey;
    }
  }

  return maxKey;
}

console.log(getMostFrequentElement(testNumbers));