Swap key with value JSON

Question

I have an extremely large JSON object structured like this:

{A : 1, B : 2, C : 3, D : 4}

I need a function that can swap the values with

Answer 1

Rewriting answer of @Vaidd4, but using Object.assign (instead of comma operator):

/**
 * Swap object keys and values
 * @param {Object<*>} obj
 * @returns {Object}
 */
function swapObject(obj) {
    return Object.keys(obj).reduce((r, key) => (Object.assign(r, {
        [obj[key]]: key,
    })), {});
}

Or, shorter:

Object.keys(obj).reduce((r, key) => (Object.assign(r, {[obj[key]]: key})), {});