Add SyntaxError explanation

Author: Zadri415

Sprint-2/1-key-errors/1.js

@@ -2,19 +2,35 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+// I predict that this program will throw a error - due to the variable decimalNumber being redeclared.
 
 // Try playing computer with the example to work out what is going on
 
-function convertToPercentage(decimalNumber) {
+/* function convertToPercentage(decimalNumber) {
   const decimalNumber = 0.5;
   const percentage = `${decimalNumber * 100}%`;
 
   return percentage;
 }
 
-console.log(decimalNumber);
+console.log(decimalNumber); */
 
 // =============> write your explanation here
+// Function covertToPercentage(decimalNumber) - it has a parameter named decimalNumber
+// Inside the function: const decimalNumber =0.5; - this redeclares the same variable name that's already used for the parameter.
+// That causes an error: SyntaxError: Identifier 'decimalNumber' has already been declared - because you can't declare a const (or let) with the same name as a parameter inside the same function scope.
+// JavaScript doesn't allow us to declare a new variable with the same name in the same scope, so it caused an error.
 
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+  return percentage;
+}
+
+console.log(convertToPercentage(0.5));
+
+// Function decimalNumber = 0.5
+// It calculates 0.5 * 100 = 50
+// it returns "50%"
+// console logs 50%