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Object prototype is a fundamental concept in JavaScript describing the mechanism by which objects inherit properties and methods from a linked object called its prototype. Each object has an internal link to another object, forming a prototype chain. The top of the chain is Object.prototype, which provides basic methods like hasOwnProperty and toString. When a property is accessed on an object, the runtime first searches the object itself, then its prototype, and so on up the chain.

Creating objects: Object.create(proto) creates a new object with the specified prototype. Object.create(null) creates a dict-like object with no prototype. The constructor pattern: a function or class defines a prototype object; instances created with new inherit from that prototype via function.prototype or Class.prototype.

Property lookup: if a property is not found on the object, the runtime checks its prototype. This is how methods are shared among instances, reducing memory usage.

Modifying prototypes: changing Object.prototype or a constructor's prototype affects all existing and future instances. This can be powerful but risks breaking libraries or code and can impact performance.

Best practices: prefer Object.getPrototypeOf(obj) over the deprecated __proto__. Use Object.create for explicit prototype control. Avoid mutating Object.prototype and be mindful of enumerable properties on prototypes. For copying objects, copy own properties rather than relying on prototype inheritance.

Prototype is a central feature of the JavaScript object model and essential for object-oriented programming in the language.