/**
 * @param {object} obj1
 * @param {object} obj2
 * @return {object}
 */
function objDiff(obj1, obj2) {
    if (obj1 === obj2) {
        return {};
    }

    if (
        obj1 === null || obj2 === null
        || typeof obj1 !== 'object' || typeof obj2 !== 'object'
        || Array.isArray(obj1) !== Array.isArray(obj2)
    ) {
        return [obj1, obj2];
    }

    let result = {};
    for (let key in obj1) {
        if (key in obj2) {
            let diff = objDiff(obj1[key], obj2[key]);
            if (Object.keys(diff).length) {
                result[key] = diff;
            }
        }
    }
    return result;
};