Find Duplicate objects in an Array of Objects in Javascript

check-duplicate.js

function checkDuplicateInObject(propertyName, inputArray) {
    let seenDuplicate = false, testObject = {};
    let dupItem = null

    inputArray.map((item) => {
        const itemPropertyName = item[propertyName];
        if (itemPropertyName in testObject) {
            testObject[itemPropertyName].duplicate = true;
            item.duplicate = true;
            seenDuplicate = true;
            dupItem = item
        }
        else {
            testObject[itemPropertyName] = item;
            delete item.duplicate;
        }
    });

    return {res:seenDuplicate, payload: dupItem};
}