diff --git a/client/i18n/locales/english/intro.json b/client/i18n/locales/english/intro.json
index 81b3e6e0d59..c656f807b97 100644
--- a/client/i18n/locales/english/intro.json
+++ b/client/i18n/locales/english/intro.json
@@ -4775,6 +4775,12 @@
         "intro": [
           "In this lab you will build a function to manage a record collection."
         ]
+      },
+      "lab-optional-arguments-sum-function": {
+        "title": "Build an Optional Arguments Sum Function",
+        "intro": [
+          "In this lab you will build a function that accepts up to two arguments, and sum them, but if there is only one argument returns a function that waits for the second number to sum."
+        ]
       }
     }
   },
diff --git a/client/src/pages/learn/full-stack-developer/lab-optional-arguments-sum-function/index.md b/client/src/pages/learn/full-stack-developer/lab-optional-arguments-sum-function/index.md
new file mode 100644
index 00000000000..5107a3e6dbc
--- /dev/null
+++ b/client/src/pages/learn/full-stack-developer/lab-optional-arguments-sum-function/index.md
@@ -0,0 +1,9 @@
+---
+title: Introduction to the Build an Optional Arguments Sum Function
+block: lab-optional-arguments-sum-function
+superBlock: full-stack-developer
+---
+
+## Introduction to the Build an Optional Arguments Sum Function
+
+In this lab you will build a function that accepts up to two arguments, and sum them, but if there is only one argument returns a function that waits for the second number to sum.
diff --git a/curriculum/challenges/english/blocks/lab-optional-arguments-sum-function/a97fd23d9b809dac9921074f.md b/curriculum/challenges/english/blocks/lab-optional-arguments-sum-function/a97fd23d9b809dac9921074f.md
new file mode 100644
index 00000000000..1f2e268ec40
--- /dev/null
+++ b/curriculum/challenges/english/blocks/lab-optional-arguments-sum-function/a97fd23d9b809dac9921074f.md
@@ -0,0 +1,120 @@
+---
+id: a97fd23d9b809dac9921074f
+title: Build an Optional Arguments Sum Function
+challengeType: 26
+dashedName: build-an-optional-arguments-sum-function
+---
+
+# --description--
+
+In this lab you will build a function that accepts up to two arguments, and sum them, but if there is only one argument returns a function that waits for the second number to sum.
+
+**Objective:** Fulfill the user stories below and get all the tests to pass to complete the lab.
+
+**User Stories:**
+
+1. Create a function `addTogether`.
+2. If the function receives two arguments, the function should return the sum of the two arguments.
+3. If only one argument is provided, `addTogether` should return a function.
+   - When the returned function is called with a single argument, it should return the sum.
+
+   ```js
+   const sumTwoAnd = addTogether(2);
+   sumTwoAnd(3); // 5
+   ```
+
+4. If either argument isn't a valid number, return `undefined`.
+
+# --hints--
+
+You should have the `addTogether` function.
+
+```js
+assert.isFunction(addTogether);
+```
+
+`addTogether(2, 3)` should return 5.
+
+```js
+assert.deepEqual(addTogether(2, 3), 5);
+```
+
+`addTogether(23.4, 30)` should return 53.4.
+
+```js
+assert.deepEqual(addTogether(23.4, 30), 53.4);
+```
+
+`addTogether("2", 3)` should return `undefined`.
+
+```js
+assert.isUndefined(addTogether('2', 3));
+```
+
+`addTogether(5, undefined)` should return `undefined`.
+
+```js
+assert.isUndefined(addTogether(5, undefined));
+```
+
+`addTogether("https://www.youtube.com/watch?v=dQw4w9WgXcQ")` should return `undefined`.
+
+```js
+assert.isUndefined(addTogether('https://www.youtube.com/watch?v=dQw4w9WgXcQ'));
+```
+
+`addTogether(5)` should return a function.
+
+```js
+assert.isFunction(addTogether(5));
+```
+
+`addTogether(5)(7)` should return 12.
+
+```js
+assert.deepEqual(addTogether(5)(7), 12);
+```
+
+`addTogether(2)([3])` should return `undefined`.
+
+```js
+assert.isUndefined(addTogether(2)([3]));
+```
+
+`addTogether(2, "3")` should return `undefined`.
+
+```js
+assert.isUndefined(addTogether(2, '3'));
+```
+
+# --seed--
+
+## --seed-contents--
+
+```js
+
+```
+
+# --solutions--
+
+```js
+function addTogether() {
+  const first = arguments[0];
+  if (typeof(first) !== 'number') {
+    return undefined;
+  }
+  if (arguments.length === 1) {
+    return function(second) {
+      if (typeof(second) !== 'number') {
+        return undefined;
+      }
+      return first + second;
+    };
+  }
+  const second = arguments[1];
+  if (typeof(second) !== 'number') {
+    return undefined;
+  }
+  return first + second;
+}
+```
diff --git a/curriculum/structure/blocks/lab-optional-arguments-sum-function.json b/curriculum/structure/blocks/lab-optional-arguments-sum-function.json
new file mode 100644
index 00000000000..dbe882da93d
--- /dev/null
+++ b/curriculum/structure/blocks/lab-optional-arguments-sum-function.json
@@ -0,0 +1,16 @@
+{
+  "name": "Build an Optional Arguments Sum Function",
+  "isUpcomingChange": false,
+  "blockType": "lab",
+  "blockLayout": "link",
+  "dashedName": "lab-optional-arguments-sum-function",
+  "superBlock": "full-stack-developer",
+  "helpCategory": "JavaScript",
+  "challengeOrder": [
+    {
+      "id": "a97fd23d9b809dac9921074f",
+      "title": "Build an Optional Arguments Sum Function"
+    }
+  ],
+  "usesMultifileEditor": true
+}
diff --git a/curriculum/structure/superblocks/full-stack-developer.json b/curriculum/structure/superblocks/full-stack-developer.json
index 3758c17980f..5fa3291a16f 100644
--- a/curriculum/structure/superblocks/full-stack-developer.json
+++ b/curriculum/structure/superblocks/full-stack-developer.json
@@ -381,6 +381,7 @@
             "lab-password-generator",
             "lab-sum-all-numbers-algorithm",
             "lab-html-entitiy-converter",
+            "lab-optional-arguments-sum-function",
             "review-javascript-fundamentals",
             "quiz-javascript-fundamentals"
           ]