Kebab file names

snippets/unflatten-object.md

@@ -0,0 +1,37 @@
+---
+title: Unflatten object
+tags: object
+cover: purple-flower-bunch
+firstSeen: 2018-02-07T11:30:18+02:00
+lastUpdated: 2020-10-22T20:24:44+03:00
+---
+
+Unflatten an object with the paths for keys.
+
+- Use nested `Array.prototype.reduce()` to convert the flat path to a leaf node.
+- Use `String.prototype.split()` to split each key with a dot delimiter and `Array.prototype.reduce()` to add objects against the keys.
+- If the current accumulator already contains a value against a particular key, return its value as the next accumulator.
+- Otherwise, add the appropriate key-value pair to the accumulator object and return the value as the accumulator.
+
+```js
+const unflattenObject = obj =>
+  Object.keys(obj).reduce((res, k) => {
+    k.split('.').reduce(
+      (acc, e, i, keys) =>
+        acc[e] ||
+        (acc[e] = isNaN(Number(keys[i + 1]))
+          ? keys.length - 1 === i
+            ? obj[k]
+            : {}
+          : []),
+      res
+    );
+    return res;
+  }, {});
+```
+
+```js
+unflattenObject({ 'a.b.c': 1, d: 1 }); // { a: { b: { c: 1 } }, d: 1 }
+unflattenObject({ 'a.b': 1, 'a.c': 2, d: 3 }); // { a: { b: 1, c: 2 }, d: 3 }
+unflattenObject({ 'a.b.0': 8, d: 3 }); // { a: { b: [ 8 ] }, d: 3 }
+```