effect-io-ai

Package: effect
Module: JsonPatch

JsonPatch.get

Computes a structural patch that transforms oldValue into newValue.

When to use

Use to compute a JSON Patch from before and after JSON documents, detect structural changes, or create deterministic update operations.

Details

Generates a structural diff between two JSON values, producing a patch that yields newValue when applied to oldValue. It returns an empty array when values are identical, recursively diffs nested structures, emits root replace operations for primitive changes, and processes object keys in sorted order for stable output.

Gotchas

Arrays are compared by index position, with no move or copy detection. Array removals are emitted from highest to lowest index to prevent index shifting. The output is deterministic but not guaranteed to be minimal.

Example (Computing object diff)

import { JsonPatch } from "effect"

const oldValue = { users: [{ id: 1, name: "Alice" }], count: 1 }
const newValue = { users: [{ id: 1, name: "Bob" }, { id: 2, name: "Charlie" }], count: 2 }

const patch = JsonPatch.get(oldValue, newValue)
// [
//   { op: "replace", path: "/users/0/name", value: "Bob" },
//   { op: "add", path: "/users/1", value: { id: 2, name: "Charlie" } },
//   { op: "replace", path: "/count", value: 2 }
// ]

See

• apply to apply the generated patch to a document
• JsonPatchOperation for the operation types in the patch

Signature

declare const get: (oldValue: Schema.Json, newValue: Schema.Json) => JsonPatch

Source

Since v4.0.0