Are Similar

Two arrays are called similar if one can be obtained from another by swapping at most one pair of elements in one of the arrays.

Given two arrays a and b, check whether they are similar.

Example
console.log(areSimilar([1, 2, 3], [1, 2, 3])); true
console.log(areSimilar([1, 2, 3], [2, 1, 3])); true
console.log(areSimilar([1, 2, 2], [2, 1, 1])); false

function areSimilar(a, b) {
  const c = [];
  let d = [];
  
  if (a.toString() === b.toString()){
    return true;
  }

  for(let i = 0;i<a.length;i++){
    if (a[i] !== b[i]) {
      c.push(a[i])
      d.push(b[i])
    }
  }
  d = d.reverse();
  if (c.length === 2 && (c.toString() === d.toString())){
    return true;
  }
  return false;

}

console.log(areSimilar([1, 2, 3], [1, 2, 3])); true
console.log(areSimilar([1, 2, 3], [2, 1, 3])); true
console.log(areSimilar([1, 2, 2], [2, 1, 1])); false

We create function called areSimilar with parameters a, b and variables c = [] and d = []

If are converting parameters a and b to string with toString() and if they are are true we return true
The toString() method returns a string representing the object. -MDN

We iterate trough array a and we check if a[i] !== b[i] we use the push method and we push them into variable arrays c and d

After that we reverse the d array with reverse method and check if c.length === 2 && (c.toString() === d.toString()) we return true otherwise we return false

The reverse() method reverses an array in place. The first array element becomes the last, and the last array element becomes the first. -MDN