Question
I have an array to find the duplicate value and their Index also

const arr = [10, 5, 8, 8, 5, 10, 6, 5, 2, 3]

Answer

const arr = [10, 5, 8, 8, 5, 10, 6, 5, 2, 3];
const duplicates = {};

for (let i = 0; i < arr.length; i++) {
const num = arr[i];

// Check if the number is already in the duplicates object
if (duplicates[num]) {
// Add the current index to the list of indices
duplicates[num].push(i);
} else {
// Initialize with the current index
duplicates[num] = [i];
}
}

// Filter out numbers with only one occurrence
const result = Object.entries(duplicates)
.filter(([key, indices]) => indices.length > 1)
.reduce((acc, [key, indices]) => {
acc[key] = indices;
return acc;
}, {});

console.log(result);

Explanation
The duplicates object maps each number to an array of its indices.As the for loop iterates through arr, it checks if the number is already in duplicates:

• If it is, the current index is added to the list.
• If it isn’t, a new array is created with the current index.

After populating duplicates, Object.entries is used to filter out numbers with only one occurrence, leaving only duplicates and their indices.