Private class fields use the # prefix for true encapsulation. Here's how to use them effectively.
Basic Syntax
Loading code block...
Private Methods
Loading code block...
Private Static Fields
Loading code block...
Private Accessors
Loading code block...
Checking for Private Fields
Loading code block...
Private Fields in Inheritance
Loading code block...
Factory Pattern with Privacy
Loading code block...
State Machine
Loading code block...
Immutable Configuration
Loading code block...
Observable with Private State
Loading code block...
Best Practices
Usage:
✓ Use # for true privacy
✓ Keep sensitive data private
✓ Hide implementation details
✓ Use private methods for internals
Patterns:
✓ Validation in private methods
✓ State management
✓ Factory methods
✓ Encapsulated logic
Benefits:
✓ True encapsulation
✓ No naming conventions needed
✓ Cannot be accessed externally
✓ Safe from prototype pollution
Avoid:
✗ Private fields in object literals
✗ Accessing via ['#name']
✗ Exposing private data in methods
✗ Over-privatizing everything
Conclusion
Private class fields with # provide true encapsulation in JavaScript. They cannot be accessed or modified from outside the class, making them ideal for sensitive data and internal implementation. Use private methods for validation and internal logic, and remember that each class has its own private namespace even in inheritance.