Untitled

function findDuplicates(chars) {
    let charCount = {};  // Object to store character counts
    let duplicates = new Set(); // Set to store characters appearing at least twice

    // Iterate through the array of characters
    for (let char of chars) {
        if (charCount[char]) { 
            // If character is already counted, add it to duplicates set
            duplicates.add(char);
        } else {
            // Otherwise, mark it as seen for the first time
            charCount[char] = 1;
        }
    }

    // Convert the set to an array and return it
    return Array.from(duplicates);
}

// Example usage
console.log(findDuplicates(['c', 'a', 'i', 'o', 'p', 'a'])); // Output: ['a']