Build a minimal PATCH payload

Compare JSON-like records deeply and emit only fields whose values changed.

MediumTypeScript Data Modeling

50 min0% acceptance

Description

Implement generic buildPatch(original, current). Compare each current or original top-level key using deep JSON-like equality, include additions and changed values, represent a removed own property with an own key whose value is undefined, and return a fresh typed Partial without changing either input.

Requirements

Export a generic buildPatch function from src/App.tsx.
Include a current own field only when it is not deeply equal to the original value.
Include fields owned only by current with their current values, including explicit undefined.
Omit primitive and nested values that are deeply equal.
Represent an original own key missing from current as an own patch key set to undefined.
Compare JSON-like arrays and plain objects recursively rather than by reference.
Return a new patch object on every call, including when no fields changed.
Preserve T in the public signature and return Partial<T> without widening field names.
Do not mutate either source object or any nested input value.

One changed field

Input

original {title:'A',meta:{pages:2}}, current {title:'B',meta:{pages:2}}

Expected output

{title:'B'}

Explanation

Deep-equal nested values are omitted even when their object identity differs.

Deleted field

Input

original owns description; current does not

Expected output

The patch owns description with value undefined

Explanation

An own undefined key distinguishes deletion from an unchanged omission.

Constraints

Compare enumerable own string keys only
Support JSON primitives, arrays, plain objects, and undefined
Array order is significant

Hints

Hint 1

Iterate the union of Object.keys from both records.

Hint 2

Use hasOwnProperty checks before comparing values so absence differs from owned undefined.

Hint 3

Keep the recursive equality helper side-effect free and treat arrays separately from objects.

TypeScriptPATCHdeep equality