Undefined to Null

Problem: 

Implement JavaScript function to return a copy that has all undefined replaced with null.

Solution: 

function undefinedToNull(data) {

if (Array.isArray(data)) {

return convertArray(data);

} else if (data === null) {

return data;

} else if (typeof data === 'object') {

return convertObject(data);

} else if (data === undefined) {

return null;

} else {

return data;

}

}

function convertArray(data) {

return data.map((element) => {

return undefinedToNull(element);

})

}

function convertObject(data) {

Object.keys(data).forEach(key => {

data[key] = undefinedToNull(data[key]);

});

return data;

}

console.log(undefinedToNull([1,4, undefined, {abc: undefined}, [{a: 1, b: 2, c: undefined}]]));