containsCommonItems.js

// Given 2 arrays, create a function that let's a user know (true/false) whether these two arrays contain any common items
//For Example:
// const array1 = ['a', 'b', 'c', 'x'];
// const array2 = ['z', 'y', 'i'];
//should return false.
//-----------
const array1 = ['a', 'b', 'c', 'x'];
const array2 = ['z', 'y', 'x'];
//should return true.

// 2 parameters - arrays - no size limit
// return true or false
function commonOne(arr1, arr2) {
  for(let i = 0; i < arr1.length; i++) {
    for(let j = 0; j < arr2.length; j++) {
      if(arr1[i] === arr2[j]) {
        return true;
      }
    }
  }
  return false;
}
//O(a*b)
//O(1) - Space Complexity

function commonTwo(arr1, arr2) {
  // loop through first array and create object where properties === items in array
  let map = {}
  for(let i = 0; i < arr1.length; i++) {
    if(!map[arr1[i]]) {
      const item = arr1[i]
      map[item] = true
    }
  }
  // loop through secdon array and check if item in second array exists on created object
  for(let j = 0; j < arr2.length; j++) {
    if(map[arr2[j]]) {
      return true;
    }
  }
  return false
}
//O(a + b) Time Complexity
//O(a) Space Complexity

//Language specific solution
function commonThree(arr1, arr2) {
  return arr1.some(item => arr2.includes(item))
}


commonOne(array1, array2)
commonTwo(array1, array2)
commonThree(array1, array2)