Add old value to changing difference (#17)

Closes #15

Author: denis-bel

README.md

@@ -52,8 +52,8 @@ const diff = require("microdiff").default;
 There are three different types of changes. `CREATE`, `REMOVE`, and `CHANGE`.
 The `path` property gives a path to the property in the new object (or the old object in the case of `REMOVE`).
 Each element in the paths is a key to the next property a level deeper until you get to the property changed, and it is string or a number, depending on whether the object is an Array or Object (Objects with number keys will still be strings).
-The `value` property exists in types `CREATE` and `CHANGE`, and it contains the value of the property added/changed.
-
+The `value` (`deletedValue` in the case of `REMOVE`) property exists in types `CREATE`, `CHANGE` and `REMOVE`, and it contains the value of the property added/changed/deleted.
+The `oldValue` property exists in the type `CHANGE`, and it contains the old value of the property changed.
 # Cycles support
 
 By default cycles are supported, but if you are sure that the object has no cycles (for example if you are parsing JSON) you can disable cycles using the `cyclesFix` option.

index.ts

@@ -2,6 +2,8 @@ interface Difference {
 	type: "CREATE" | "REMOVE" | "CHANGE";
 	path: (string | number)[];
 	value?: any;
+	oldValue?: any;
+	deletedValue?: any;
 }
 interface Options {
 	cyclesFix: boolean;
@@ -26,6 +28,7 @@ export default function diff(
 			diffs.push({
 				type: "REMOVE",
 				path: [path],
+				deletedValue: obj[key]
 			});
 			continue;
 		}
@@ -65,6 +68,7 @@ export default function diff(
 				path: [path],
 				type: "CHANGE",
 				value: newObjKey,
+				oldValue: objKey
 			});
 		}
 	}