The override keyword in TypeScript is used to explicitly indicate that a method in a subclass is intended to override a method in its superclass. This keyword was introduced in TypeScript version 4.3 to enhance code clarity and help prevent errors during development.
How the override Keyword Functions
Explicit Declaration: When you use the override keyword in a subclass method, it clearly states that the method is meant to replace a method in the superclass. This makes the developer's intention clear, improving code readability and maintainability[1][3].
Compiler Verification: The TypeScript compiler plays a crucial role when the override keyword is used. It checks to ensure that the overridden method exists in the superclass with the same name and signature. If the superclass does not have a method with the same name, or if there is a mismatch in the method signature, the compiler will throw an error. This prevents issues such as typos or misunderstandings about the superclass's method names, which could lead to bugs[1][3].
Error Prevention: By forcing the developer to use the override keyword when overriding methods, TypeScript provides a safeguard against common errors. For example, if a method in the superclass is removed or renamed, the TypeScript compiler will immediately flag the overriding method in the subclass as an error if it still uses the override keyword. This immediate feedback loop helps developers catch and fix issues early in the development process[1][3].
Practical Example
Consider a simple example with a superclass Animal and a subclass Dog:
