prototypal

Prototypal refers to a style of object-oriented programming in which objects inherit directly from other objects rather than from classes. The concept originated in language designs such as Self and Smalltalk and became widely known through JavaScript, where objects can have a prototype chain linking them to ancestor objects. In a prototypal system, a new object is created by specifying an existing object as its prototype, and the new object can delegate property lookup to its prototype if it does not contain the requested property itself. This delegation mechanism allows for dynamic extension of objects and flexible sharing of behavior.

Prototypal inheritance replaces the traditional class-based hierarchy with prototype chains. When a property is accessed, the runtime walks up the prototype chain until it finds a matching property or reaches the end. Methods can be shared across all instances by storing them on a prototype object, while instance-specific data stays on the object itself. This model supports features such as mixins, delegation, and dynamic prototype mutation, enabling very flexible design patterns.

In JavaScript, the native Object.create method creates an object with a specified prototype, while the variable prototype property of functions (new.target.prototype) allows constructor functions to define instance methods. Modern frameworks and libraries sometimes expose higher-level abstractions (e.g., ES6 class syntax) that compile to prototypal patterns, but the underlying mechanics remain the same.

The prototypal approach offers memory efficiency for shared methods and easier runtime composition. However, it can lead to less predictable inheritance hierarchies, making debugging more challenging. Prototypal inheritance remains a fundamental concept for languages that embrace delegation over class-based design.