How to Avoid Unexpected Behavior When Modifying Nested Objects in Crockford's Prototypal Inheritance?

Crockford's Prototypal Inheritance: Addressing Nesting Concerns

Douglas Crockford's concept of prototypal inheritance provides a simplified approach to object creation, as exemplified in the "Object.create" function. However, users may encounter difficulties when dealing with nested objects in this inheritance framework. Specifically, overwriting nested object values can affect other objects along the prototype chain, leading to unexpected results.

To illustrate the concern, consider the following code snippet:

// Flat object
var flatObj = {
    firstname: "John",
    lastname: "Doe",
    age: 23
}

// Nested object
var nestObj = {
    sex: "female",
    info: {
        firstname: "Jane",
        lastname: "Dough",
        age: 32  
    }
}

In this scenario, creating new objects using "Object.create" and attempting to modify nested object values results in unintended changes to the prototype objects:

// Objects created using Object.create
var person1 = Object.create(flatObj);  // Flat object inheritance
var person2 = Object.create(nestObj);  // Nested object inheritance

// Overwriting nested object values
person1.age = 69;
person2.info.age = 96;

// Prototype objects have been modified
console.log(nestObj.info.age);  // Outputs 96 instead of 32

The core issue stems from the fact that all objects, including nested ones, are treated like standard object properties. When modifying a nested object value, the change is propagated not only to the current object but also to any other objects that inherit from the same prototype.

Therefore, if you wish to maintain independent nested objects, it's crucial to create new objects for them instead of relying on inheritance. For example:

// Creating an independent nested object
person3 = {
    sex: "male",
    info: Object.create(nestObj2.info)  // Create a new object for the nested "info" property
}

By doing so, you ensure that changes to nested object values only affect the specific object and do not propagate up the prototype chain.

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