Move arrow functions concept to different exercise

config.json

@@ -108,14 +108,8 @@
         "slug": "elyses-analytic-enchantments",
         "name": "Elyses Analytic Enchantments",
         "uuid": "45d956db-d4ef-4468-b1d3-47021f172c15",
-        "concepts": ["array-analysis"],
-        "prerequisites": [
-          "arrays",
-          "arrow-functions",
-          "booleans",
-          "callbacks",
-          "numbers"
-        ],
+        "concepts": ["arrow-functions", "array-analysis"],
+        "prerequisites": ["arrays", "booleans", "callbacks", "numbers"],
         "status": "beta"
       },
       {
@@ -181,7 +175,7 @@
         "slug": "fruit-picker",
         "name": "Fruit Picker",
         "uuid": "a6348db8-cc2b-4c53-9f43-3c23248d66f0",
-        "concepts": ["arrow-functions", "callbacks"],
+        "concepts": ["callbacks"],
         "prerequisites": ["functions", "objects"],
         "status": "beta"
       },

exercises/concept/elyses-analytic-enchantments/.docs/introduction.md

@@ -1,5 +1,42 @@
 # Introduction
 
+## Arrow Functions
+
+Besides function declarations and function expressions, JavaScript also has another very concise syntax for defining a function.
+These functions are called _arrow functions_.
+
+Here is a comparison between a function declaration and an arrow function.
+
+```javascript
+function addUpTwoNumbers(num1, num2) {
+  return num1 + num2;
+}
+// function keyword removed and => added
+const addUpTwoNumbers = (num1, num2) => {
+  return num1 + num2;
+};
+```
+
+If the function body contains only a return statement, like in the example above, the `{}` and the `return` keyword can be omitted.
+If there is only one parameter, the parenthesis `()` can be omitted as well.
+
+<!-- prettier-ignore-start -->
+```javascript
+const addUpTwoNumbers = (num1, num2) => num1 + num2;
+const square = num => num * num;
+```
+<!-- prettier-ignore-end -->
+
+Arrow functions are often used to define short callback functions directly in the function call.
+
+<!-- prettier-ignore-start -->
+```javascript
+applyToSquare(number => number * number);
+```
+<!-- prettier-ignore-end -->
+
+## Array Analysis
+
 [Arrays][arrays-concept] have built-in methods to analyse the contents of the array.
 Most of these methods take a function that returns true or false as an argument.
 Such a function is called a [`predicate`][predicate_in_programming].
@@ -28,7 +65,7 @@ numbers.indexOf('two');
 
 Some other helpful built-in methods that are available to analyze an array are shown below. See [MDN][mdn-array-methods] for a full list of array methods.
 
-## `includes`
+### `includes`
 
 > The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate. [^1]
 
@@ -40,7 +77,7 @@ numbers.includes('one');
 // => false
 ```
 
-## `every`
+### `every`
 
 > The every() method tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value. [^2]
 
@@ -50,7 +87,7 @@ numbers.every((num) => num % 2 !== 0);
 // => true
 ```
 
-## `some`
+### `some`
 
 > The some() method tests whether at least one element in the array passes the test implemented by the provided function. [^3]
 
@@ -60,7 +97,7 @@ numbers.some((num) => num % 2 !== 0);
 // => true
 ```
 
-## `find`
+### `find`
 
 > The find() method returns the value of the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned. [^4]
 
@@ -70,7 +107,7 @@ numbers.find((num) => num < 5);
 // => 1
 ```
 
-## `findIndex`
+### `findIndex`
 
 > The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise, it returns -1, indicating that no element passed the test. [^5]