problems(js): add “2633. Convert Object to JSON String”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/js/convert-object-to-json-string.js

@@ -0,0 +1,25 @@
+/**
+ * @param {any} object
+ * @return {string}
+ */
+var jsonStringify = function(object) {
+    switch (typeof object) {
+        case 'boolean':
+        case 'number':
+            return `${object}`;
+        case 'string':
+            return `"${object}"`;
+        case 'object':
+            if (Array.isArray(object)) {
+                return `[${object.map(jsonStringify).join(',')}]`;
+            }
+
+            if (object) {
+                let nested = Object.keys(object).map(key => `"${key}":${jsonStringify(object[key])}`);
+                return `{${nested.join(',')}}`;
+            }
+            return 'null';
+        default:
+            return '';
+    }
+};