Interview question - Big O

// 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 containsCommonItem(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

const array1 = ['a', 'b', 'c', 'x'];
const array2 = ['z', 'y', 'a'];

function containsCommonItem2(arr1, arr2) {
  // loop through first array and create object where properties === items in the array
  // can we assume always 2 params?

  let map = {};
  for (let i=0; i < arr1.length; i++) {
    if(!map[arr1[i]]) {
      const item = arr1[i];
      map[item] = true;
    }
  }
  // loop through second 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

// containsCommonItem2(array1, array2)

function containsCommonItem3(arr1, arr2) {
  return arr1.some(item => arr2.includes(item))
}

containsCommonItem(array1, array2)
containsCommonItem2(array1, array2)
containsCommonItem3(array1, array2)