Add solution #2705

Author: JoshCrozier

README.md

@@ -407,6 +407,7 @@
 2677|[Chunk Array](./2677-chunk-array.js)|Easy|
 2695|[Array Wrapper](./2695-array-wrapper.js)|Easy|
 2703|[Return Length of Arguments Passed](./2703-return-length-of-arguments-passed.js)|Easy|
+2705|[Compact Object](./2705-compact-object.js)|Medium|
 2715|[Timeout Cancellation](./2715-timeout-cancellation.js)|Easy|
 2721|[Execute Asynchronous Functions in Parallel](./2721-execute-asynchronous-functions-in-parallel.js)|Medium|
 2722|[Join Two Arrays by ID](./2722-join-two-arrays-by-id.js)|Medium|

solutions/2705-compact-object.js

@@ -0,0 +1,32 @@
+/**
+ * 2705. Compact Object
+ * https://leetcode.com/problems/compact-object/
+ * Difficulty: Medium
+ *
+ * Given an object or array obj, return a compact object.
+ *
+ * A compact object is the same as the original object, except with keys containing falsy
+ * values removed. This operation applies to the object and any nested objects. Arrays are
+ * considered objects where the indices are keys. A value is considered falsy when
+ * Boolean(value) returns false.
+ *
+ * You may assume the obj is the output of JSON.parse. In other words, it is valid JSON.
+ */
+
+/**
+ * @param {Object|Array} obj
+ * @return {Object|Array}
+ */
+var compactObject = function(obj) {
+  if (obj === null) return null;
+  if (Array.isArray(obj)) return obj.filter(Boolean).map(compactObject);
+  if (typeof obj !== 'object') return obj;
+
+  return Object.keys(obj).reduce((result, key) => {
+    const value = compactObject(obj[key]);
+    if (value) {
+      result[key] = value;
+    }
+    return result;
+  }, {});
+};