feat(curriculum): add Build a Missing Letter Detector lab (#62227)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

client/i18n/locales/english/intro.json

@@ -3369,6 +3369,12 @@
           "In this lab, you will implement loops to repeat a string a specified number of times."
         ]
       },
+      "lab-missing-letter-detector": {
+        "title": "Build a Missing Letter Detector",
+        "intro": [
+          "In this lab, you will build a function that finds the missing letter in a given range of consecutive letters and returns it."
+        ]
+      },
       "review-javascript-loops": {
         "title": "JavaScript Loops Review",
         "intro": [

client/src/pages/learn/full-stack-developer/lab-missing-letter-detector/index.md

@@ -0,0 +1,9 @@
+---
+title: Introduction to the Build a Missing Letter Detector
+block: lab-missing-letter-detector
+superBlock: full-stack-developer
+---
+
+## Introduction to the Build a Missing Letter Detector
+
+For this lab, you will create a function that finds the missing letter in a given range of consecutive letters and returns it.

curriculum/challenges/english/blocks/lab-missing-letter-detector/af7588ade1100bde429baf20.md

@@ -0,0 +1,78 @@
+---
+id: af7588ade1100bde429baf20
+title: Build a Missing Letter Detector
+challengeType: 26
+dashedName: build-a-missing-letter-detector
+---
+
+# --description--
+
+**Objective:** Fulfill the user stories below and get all the tests to pass to complete the lab.
+
+**User Stories:**
+
+1. You should have a function named `fearNotLetter`.
+1. The `fearNotLetter` function should accept one argument: a string representing a range of letters.
+1. The function should find the missing letter in the passed letter range and return it.
+1. If all letters are present in the range, the function should return `undefined`.
+
+# --hints--
+
+You should have a `fearNotLetter` function.
+
+```js
+assert.isFunction(fearNotLetter);
+```
+
+`fearNotLetter("abce")` should return the string `d`.
+
+```js
+assert.deepEqual(fearNotLetter('abce'), 'd');
+```
+
+`fearNotLetter("abcdefghjklmno")` should return the string `i`.
+
+```js
+assert.deepEqual(fearNotLetter('abcdefghjklmno'), 'i');
+```
+
+`fearNotLetter("stvwx")` should return the string `u`.
+
+```js
+assert.deepEqual(fearNotLetter('stvwx'), 'u');
+```
+
+`fearNotLetter("bcdf")` should return the string `e`.
+
+```js
+assert.deepEqual(fearNotLetter('bcdf'), 'e');
+```
+
+`fearNotLetter("abcdefghijklmnopqrstuvwxyz")` should return `undefined`.
+
+```js
+assert.isUndefined(fearNotLetter('abcdefghijklmnopqrstuvwxyz'));
+```
+
+# --seed--
+
+## --seed-contents--
+
+```js
+
+```
+
+# --solutions--
+
+```js
+function fearNotLetter (str) {
+  for (var i = str.charCodeAt(0); i <= str.charCodeAt(str.length - 1); i++) {
+    let letter = String.fromCharCode(i);
+    if (str.indexOf(letter) === -1) {
+      return letter;
+    }
+  }
+
+  return undefined;
+}
+```

curriculum/structure/blocks/lab-missing-letter-detector.json

@@ -0,0 +1,15 @@
+{
+  "name": "Build a Missing Letter Detector",
+  "blockType": "lab",
+  "blockLayout": "link",
+  "isUpcomingChange": false,
+  "usesMultifileEditor": true,
+  "dashedName": "lab-missing-letter-detector",
+  "challengeOrder": [
+    {
+      "id": "af7588ade1100bde429baf20",
+      "title": "Build a Missing Letter Detector"
+    }
+  ],
+  "helpCategory": "JavaScript"
+}

curriculum/structure/superblocks/full-stack-developer.json

@@ -366,6 +366,7 @@
             "lab-chunky-monkey",
             "lab-profile-lookup",
             "lab-repeat-a-string",
+            "lab-missing-letter-detector",
             "review-javascript-loops",
             "quiz-javascript-loops"
           ]