Complete Sprint 3 section 1: errors

Author: BrianY315

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

@@ -1,13 +1,18 @@
 // Predict and explain first...
-//  =============> write your prediction here
+// Prediction: Node will report a SyntaxError because str is declared twice in
+// the same function scope: once as a parameter and again with let.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
 
+// Faulty line from the original: let str = `${str[0].toUpperCase()}${str.slice(1)}`;
+
+// Error: SyntaxError: Identifier 'str' has already been declared
+// Explanation: A function parameter is already a binding in the function body.
+// Declaring another let binding with the same name is not allowed.
+// Corrected code:
 function capitalise(str) {
-  let str = `${str[0].toUpperCase()}${str.slice(1)}`;
-  return str;
+  return `${str[0].toUpperCase()}${str.slice(1)}`;
 }
 
-// =============> write your explanation here
-// =============> write your new code here
+console.log(capitalise("hello"));

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

@@ -1,20 +1,23 @@
 // Predict and explain first...
 
 // Why will an error occur when this program runs?
-// =============> write your prediction here
+// Prediction: Node will report a SyntaxError because decimalNumber is declared
+// as a const inside the function even though it is already a parameter.
 
 // Try playing computer with the example to work out what is going on
 
-function convertToPercentage(decimalNumber) {
-  const decimalNumber = 0.5;
-  const percentage = `${decimalNumber * 100}%`;
-
-  return percentage;
-}
-
-console.log(decimalNumber);
+// Faulty original lines:
+// const decimalNumber = 0.5; // duplicates the parameter inside the function
+// console.log(decimalNumber); // refers to the parameter outside its scope
 
-// =============> write your explanation here
+// Error: SyntaxError: Identifier 'decimalNumber' has already been declared
+// Explanation: The parameter already declares decimalNumber in the function
+// scope. The inner const declaration duplicates that binding. Also, the final
+// console.log refers to a name that would not be available outside the function.
 
 // Finally, correct the code to fix the problem
-// =============> write your new code here
+function convertToPercentage(decimalNumber) {
+  return `${decimalNumber * 100}%`;
+}
+
+console.log(convertToPercentage(0.5));

Sprint-3/1-key-errors/2.js

@@ -3,18 +3,22 @@
 
 // this function should square any number but instead we're going to get an error
 
-// =============> write your prediction of the error here
+// Prediction: Node will report a SyntaxError because a number cannot be used
+// as a function parameter name.
 
-function square(3) {
-    return num * num;
-}
+// Faulty original: function square(3) { return num * num; }
 
-// =============> write the error message here
+// Error: SyntaxError: Unexpected number
 
-// =============> explain this error message here
+// Explanation: Function parameters must be identifiers such as num, not literal
+// values such as 3. The body also refers to num, which was never declared.
 
 // Finally, correct the code to fix the problem
 
-// =============> write your new code here
+function square(num) {
+    return num * num;
+}
+
+console.log(square(3));