Kebab file names

snippets/deep-clone.md

@@ -0,0 +1,38 @@
+---
+title: Deep clone object
+tags: object,recursion
+cover: neon-desk-2
+firstSeen: 2018-01-23T20:48:46+02:00
+lastUpdated: 2020-10-22T20:23:47+03:00
+---
+
+Creates a deep clone of an object.
+Clones primitives, arrays and objects, excluding class instances.
+
+- Use recursion.
+- Check if the passed object is `null` and, if so, return `null`.
+- Use `Object.assign()` and an empty object (`{}`) to create a shallow clone of the original.
+- Use `Object.keys()` and `Array.prototype.forEach()` to determine which key-value pairs need to be deep cloned.
+- If the object is an `Array`, set the `clone`'s `length` to that of the original and use `Array.from()` to create a clone.
+
+```js
+const deepClone = obj => {
+  if (obj === null) return null;
+  let clone = Object.assign({}, obj);
+  Object.keys(clone).forEach(
+    key =>
+      (clone[key] =
+        typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
+  );
+  if (Array.isArray(obj)) {
+    clone.length = obj.length;
+    return Array.from(clone);
+  }
+  return clone;
+};
+```
+
+```js
+const a = { foo: 'bar', obj: { a: 1, b: 2 } };
+const b = deepClone(a); // a !== b, a.obj !== b.obj
+```