Fix redeclaration error in capitalise function

Remove redeclaration of 'str' in capitalise function.

Author: mrafeie

Sprint-3/1-key-errors/0.js

@@ -1,7 +1,9 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// I predict this code will produce a SyntaxError because str is declared twice in the same scope using let.
 
 // call the function capitalise with a string input
+capitalise("hello");
 // interpret the error message and figure out why an error is occurring
 
 function capitalise(str) {
@@ -10,4 +12,14 @@ function capitalise(str) {
 }
 
 // =============> write your explanation here
+// The error occurs because str is already declared as a parameter
+// Inside the function, let str attempts to declare another variable
+// with the same name in the same scope.
+// We can fix the problem by removing let and assigning the new value
+// directly to the existing parameter.
+
 // =============> write your new code here
+function capitalise(str) {
+  str = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return str;
+}