Improve lab handling-errors.html

docs/labs/handling-errors.html

@@ -83,7 +83,10 @@
   - - "  return { result: a / b };"
 - index: 2
   absent: '\s*try\s*{\s* '
-  text: Use a try block to catch any exceptions that might be thrown.
+  text: >-
+    Use a try block to catch any exceptions that might be thrown.
+    It should look something like `try { ... } catch(err) {...}`
+    (fill in the `...` sections).
   examples:
   - - "  const result = divide(10, 2);"
 - index: 2
@@ -98,7 +101,9 @@
   - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result.result ); "
 - index: 2
   absent: '.*? catch .*? '
-  text: Handle the error within the catch block.
+  text: >-
+    Handle the error within the catch block. You need `catch(err) {...}`
+    after `try {...}` to catch an error in the try block.
   examples:
   - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result ); }"
 - index: 2
@@ -107,10 +112,25 @@
   examples:
   - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result ); } catch {}"
 - index: 2
-  absent: '\s* catch \s* \( err \) { \s* '
-  text: Catch an object named err within the catch block.
+  absent: |-
+    catch \( err \)
+  text: >-
+    Please use `catch(err) {...}` for purposes of this lab.
   examples:
   - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result ); } catch (foo) {"
+- index: 2
+  present: |-
+    catch .* console \. error \( ["'][^"']*["'] , result
+  text: >-
+    When reporting the error, you need to report it in the catch block,
+    which catches it as the variable `err`.
+    Thus, you need to use `err.message` not `result` or `result.message`,
+    since the error is in `err.message`. Note that 
+    the variable `result` is out of scope in the catch block anyway;
+    it was declared in the try block.
+  examples:
+  - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result ); } catch (err) { console.error('Error', result.message);"
+  - - " try { const result = divide(10 ,2); console.log ( \"Result:\", result ); } catch (err) { console.error('Error', result );"
 # debug: true
 </script>
 </head>