docs: improve formatting and explanation for accidental global example

coding-exercise/accidental-global.js

@@ -1,24 +1,32 @@
 function foo() {
-  let x = (y = 0);
+  let x = (y = 0); // ⚠️ y becomes a global variable
   x++;
   y++;
   return x;
 }
 
-console.log(foo(), typeof x, typeof y); //  1, undefined, number
+console.log(foo(), typeof x, typeof y);
+// Output: 1, "undefined", "number"
 
 /**
- * Here's the breakdown:
-    1. Inside the foo function, x is declared using let, which means it's scoped to the function. However, y is not declared with let or var, so it becomes a global variable.
-
-    2. When x = y = 0; is executed, it's interpreted as x = (y = 0);, which initializes y as a global variable with the value of 0, and x as a local variable within the function with the value of 0.
-
-    3. x++ increments the local variable x by 1, making it 1.
-
-    4. y++ increments the global variable y by 1, making it 1 as well.
-
-    5. The function returns the value of x, which is 1.
-
-    However, x is scoped within the function, so typeof x outside of the function will result in undefined.
-    y is a global variable, so typeof y outside of the function will result in number.
- */
+ * Explanation:
+ *
+ * 1. `x` is declared using `let`, so it is scoped to the `foo` function.
+ *
+ * 2. `y` is NOT declared using `let`, `var`, or `const`.
+ *    This causes `y` to become a global variable.
+ *
+ * 3. The expression `x = (y = 0)` is evaluated right to left:
+ *    - `y` is assigned `0` (global)
+ *    - `x` is assigned the value of `y` (local)
+ *
+ * 4. `x++` increments the local variable `x` → 1
+ *
+ * 5. `y++` increments the global variable `y` → 1
+ *
+ * 6. The function returns `x`, which is `1`.
+ *
+ * Outside the function:
+ * - `typeof x === "undefined"` (x is function-scoped)
+ * - `typeof y === "number"` (y is global)
+ */