How to Find Matching Elements Across Multiple JavaScript Arrays?

Matching Elements Across Multiple JavaScript Arrays

Problem

Given multiple JavaScript arrays of string values, find the elements that occur identically in all the arrays. For example:

<code class="javascript">var arr1 = ['apple', 'orange', 'banana', 'pear', 'fish', 'pancake', 'taco', 'pizza'];
var arr2 = ['taco', 'fish', 'apple', 'pizza'];
var arr3 = ['banana', 'pizza', 'fish', 'apple'];</code>

Expected output:

<code class="javascript">['apple', 'fish', 'pizza']</code>

Solution

To find the matching elements, we can use a combination of Array methods:

<code class="javascript">const arrays = [arr1, arr2, arr3];
const result = arrays.shift().filter((v) => {
  return arrays.every((a) => {
    return a.indexOf(v) !== -1;
  });
});</code>

Steps:

1. Use arrays.shift() to remove the first array from the original list.
2. Use .filter() on the first array to loop through each element v.
3. Use .every() on the rest of the arrays to check if each one contains the current element v.
4. If the element v is present in every array, include it in the result array.

By iteratively applying this logic to each array, we can effectively find the elements that occur identically in all the provided arrays.

Additional Considerations

Duplicate Element Handling:

The provided solution assumes that the arrays do not contain duplicate elements. If they do, you can modify the code as follows:

<code class="javascript">const result = arrays.shift().reduce((res, v) => {
  if (res.indexOf(v) === -1 &amp;&amp; arrays.every((a) => {
    return a.indexOf(v) !== -1;
  })) res.push(v);
  return res;
}, []);</code>

This code uses .reduce() instead of .filter(). It checks for duplicates within the result array and only adds unique elements that are present in every array.

Arbitrary Number of Arrays:

The solution is designed to work with an unknown number of arrays. By using arrays.shift(), we can sequentially compare the first array to the remaining arrays until all arrays have been processed.

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