Salesforce JavaScript Developer Practice Exam

What is the difference between a function's prototype and an object's prototype?

1. A function's prototype is specific to instances of the function

2. An object's prototype determines its properties only

3. Both prototypes can be assigned independently

4. A function's prototype is the object instance that will become the prototype for constructed objects

The correct answer is: A function's prototype is the object instance that will become the prototype for constructed objects

A function's prototype serves a crucial role in the JavaScript prototype chain, particularly in relation to object creation. When a function is defined, it automatically gets a prototype object. This prototype object contains properties and methods that should be available to any object instances created through that function. When a new object is created using a constructor function, that object's internal [[Prototype]] (accessible via `Object.getPrototypeOf()`) is set to the constructor function’s prototype. This essentially means that all instances created from that function inherit the properties and methods defined on the function's prototype. In this context, the correct choice highlights that the prototype associated with a function is what determines the properties and methods available to the objects created from that function. This is foundational to JavaScript's prototypal inheritance and enables code reuse and organization. The other options do not accurately convey the relationship between functions and prototypes in JavaScript. Some may misinterpret the nature of prototypes, while others may imply a misunderstanding of the inheritance mechanism in JavaScript. Understanding this distinction makes it clear how prototypes work in the context of functions and object creation, which is key to mastering JavaScript's behavior regarding objects and inheritance.