This code in Libraries/Utilities/differ/deepDiffer.js triggers the warning mentioned in #869
for (var key in one) {
if (deepDiffer(one[key], two[key])) {
return true;
}
}
for (var twoKey in two) {
// The only case we haven't checked yet is keys that are in two but aren't
// in one, which means they are different.
if (one[twoKey] === undefined && two[twoKey] !== undefined) {
return true;
}
}