Write a function to find duplicate chararcter in Java Script

simple JavaScript function to find duplicate characters in a string

function findDuplicateCharacters(str) {
    let charCount = {};
    let duplicates = [];

    // Loop through the string and count the occurrences of each character
    for (let char of str) {
        charCount[char] = (charCount[char] || 0) + 1;
    }

    // Find characters that appear more than once
    for (let char in charCount) {
        if (charCount[char] > 1) {
            duplicates.push(char);
        }
    }

    return duplicates;
}

// Example usage:
let result = findDuplicateCharacters("programming");
console.log(result); // Output: [ 'r', 'g', 'm' ]

Explanation:

1. charCount: This object will store each character of the string as a key and the number of times it appears as the value.
2. duplicates: This array will store characters that appear more than once in the string.
3. First Loop: We loop through the string to count how many times each character appears.
4. Second Loop: We check for characters that appear more than once and add them to the duplicates array.

This function will return an array of duplicate characters found in the input string.