Map anagrams to one another in JavaScript

One array is an anagram of another if we can rearrange the elements of that array to achieve the other array.

For example:

[1, 2, 3] and [2, 1, 3] are anagrams of each other.

We need to write a JavaScript function that takes two anagram arrays and returns a mapping array. The mapping array contains the index of each element from the first array as it appears in the second array.

Problem Example

If the two input arrays are:

const arr1 = [23, 39, 57, 43, 61];
const arr2 = [61, 23, 43, 57, 39];

Then the output should be:

const output = [1, 4, 3, 2, 0];

This means:

• Item at index 0 in arr1 (23) is at index 1 in arr2
• Item at index 1 in arr1 (39) is at index 4 in arr2
• Item at index 2 in arr1 (57) is at index 3 in arr2
• And so on...

Using Nested Loops

const arr1 = [23, 39, 57, 43, 61];
const arr2 = [61, 23, 43, 57, 39];

const anagramMappings = (arr1 = [], arr2 = []) => {
    const res = [];
    for (let i = 0; i < arr1.length; i++) {
        for (let j = 0; j < arr2.length; j++) {
            if (arr1[i] == arr2[j]) {
                res.push(j);
                break; // Exit inner loop once found
            }
        }
    }
    return res;
};

console.log(anagramMappings(arr1, arr2));

[ 1, 4, 3, 2, 0 ]

Using indexOf() Method

A more concise approach uses the built-in indexOf() method:

const arr1 = [23, 39, 57, 43, 61];
const arr2 = [61, 23, 43, 57, 39];

const anagramMappingsIndexOf = (arr1 = [], arr2 = []) => {
    return arr1.map(element => arr2.indexOf(element));
};

console.log(anagramMappingsIndexOf(arr1, arr2));

[ 1, 4, 3, 2, 0 ]

Comparison

Conclusion

Both approaches solve the anagram mapping problem effectively. The indexOf() method provides cleaner, more readable code while maintaining the same functionality.