Rename js snippets

snippets/js/s/nest-objects.md

@@ -0,0 +1,35 @@
+---
+title: Nest objects
+type: snippet
+language: javascript
+tags: [object,recursion]
+cover: birds
+dateModified: 2020-10-21T21:54:53+03:00
+---
+
+Nests recursively objects linked to one another in a flat array.
+
+- Use recursion.
+- Use `Array.prototype.filter()` to filter the items where the `id` matches the `link`.
+- Use `Array.prototype.map()` to map each item to a new object that has a `children` property which recursively nests the items based on which ones are children of the current item.
+- Omit the second argument, `id`, to default to `null` which indicates the object is not linked to another one (i.e. it is a top level object).
+- Omit the third argument, `link`, to use `'parent_id'` as the default property which links the object to another one by its `id`.
+
+```js
+const nest = (items, id = null, link = 'parent_id') =>
+  items
+    .filter(item => item[link] === id)
+    .map(item => ({ ...item, children: nest(items, item.id, link) }));
+```
+
+```js
+const comments = [
+  { id: 1, parent_id: null },
+  { id: 2, parent_id: 1 },
+  { id: 3, parent_id: 1 },
+  { id: 4, parent_id: 2 },
+  { id: 5, parent_id: 4 }
+];
+const nestedComments = nest(comments);
+// [{ id: 1, parent_id: null, children: [...] }]
+```