Understanding Error Objects in JavaScript

Overview of Error Objects

• Today's lecture focuses on error objects in JavaScript.
• We'll cover how error objects work, how to throw custom errors, and examples of usage.

Key Concepts

• Error Object Properties
  • name: Type of error (e.g., ReferenceError, SyntaxError)
  • message: Description of the error
  • stack: Provides a stack trace (less commonly used)

Demonstration of Error Objects

1. Creating a New Repl
   • Project name example: 61_error_object
2. Using Try-Catch
   • Example with an undefined variable:

     try {
         console.log(harry);
     } catch (error) {
         console.log(error.name);   // Outputs: ReferenceError
         console.log(error.message); // Outputs: "harry is not defined"
     }
     

3. Throwing Custom Errors
   • To throw a custom error:

     throw new Error("Harry is not good");
     

   • Throwing a ReferenceError example:

     throw new ReferenceError("Harry is not good");
     

Custom Error Example with Age Validation

1. Prompting User Input
   • Example code:

     let age = prompt("Enter your age");
     age = Number.parseInt(age);
     if (age > 120) {
         throw new Error("This is probably not true");
     }
     

2. Error Handling
   • Use try-catch to manage errors:

     try {
         // code that may throw an error
     } catch (error) {
         console.log(error.message);
         console.log(error.stack);
     }
     

Types of Errors in JavaScript

• Common errors include:
  • SyntaxError
  • ReferenceError
  • RangeError
  • Internal Error
• More details can be found on MDN documentation regarding JavaScript errors.

Conclusion

• Understanding how to handle and throw errors is crucial for robust coding in JavaScript.
• In the next video, the topic of "clause" will be addressed, including its practical use cases.
• If you encounter difficulties with the Replit environment, access the JavaScript playlist on Replit to find all necessary resources: replit.com/@codewithharry.

Additional Resources

• Access the Ultimate JavaScript Course folder to clone and run examples directly.