our own json patch lib and everything working

client/lib/json-patch-lib.ts

@@ -0,0 +1,86 @@
+export interface Validator<T> {
+  (operation: Operation, index: number, document: T, existingPathFragment: string): void
+}
+
+export interface BaseOperation {
+  path: string
+}
+
+export interface AddOperation<T> extends BaseOperation {
+  op: 'add'
+  value: T
+}
+
+export interface RemoveOperation extends BaseOperation {
+  op: 'remove'
+}
+
+export interface ReplaceOperation<T> extends BaseOperation {
+  op: 'replace'
+  value: T
+}
+
+export type Doc = { [key: string]: any }
+
+export type Operation = AddOperation<any> | RemoveOperation | ReplaceOperation<any>
+
+export function getValueByPointer (document: any, pointer: string): any {
+  const pathArr = pointer.split('/')
+  pathArr.shift()
+  try {
+    return pathArr.reduce((acc, next) => acc[next], document)
+  } catch (e) {
+    return undefined
+  }
+}
+
+export function applyOperation (document: Doc, op: Operation): Operation | null {
+  let undo: Operation | null = null
+  const pathArr = op.path.split('/')
+  pathArr.shift()
+  pathArr.reduce((node, key, i) => {
+    if (!isObject) {
+      throw Error('patch cannot be applied.  Path contains non object')
+    }
+
+    if (i < pathArr.length - 1) {
+      // iterate node
+      return node[key]
+    }
+
+    // if last key
+    const curVal = node[key]
+    if (op.op === 'add' || op.op === 'replace') {
+      node[key] = op.value
+      if (curVal) {
+        undo = {
+          op: 'replace',
+          path: op.path,
+          value: curVal,
+        }
+      } else {
+        undo = {
+          op: 'remove',
+          path: op.path,
+        }
+      }
+    } else {
+      delete node[key]
+      if (curVal) {
+        undo = {
+          op: 'add',
+          path: op.path,
+          value: curVal,
+        }
+      }
+    }
+  }, document)
+
+  return undo
+}
+
+function isObject (val: any): val is Doc {
+  return typeof val === 'object' && !Array.isArray(val) && val !== null
+}
+
+