What\'s the Difference Between proto and constructor.prototype in JavaScript Inheritance?

Understanding the Difference Between proto and constructor.prototype

It's important to understand the distinction between the __proto__ property and constructor.prototype when working with JavaScript objects.

proto and Prototype Chain

Every JavaScript object has an internal __proto__ property that references the prototype object of its constructor. This prototype object contains the shared properties and methods for objects of its type.

Demonstration

Consider the following code:

<code class="js">function Gadget(name, color) {
  this.name = name;
  this.color = color;
}

Gadget.prototype.rating = 3;

var newtoy = new Gadget("webcam", "black");</code>

In this example, newtoy's __proto__ would point to Gadget.prototype, which has the rating property with a value of 3. Thus, accessing newtoy.__proto__.__proto__.__proto__ would return null as it has no further prototype object.

constructor.prototype.constructor.prototype

This complex expression does not directly access the prototype chain. Instead, it attempts to access the constructor.prototype of the constructor.prototype of the constructor.prototype of the Gadget constructor. In this case, it's the Gadget constructor itself. Hence, it keeps pointing to Gadget.prototype.

Checking for Null in Internet Explorer

Internet Explorer does not support the __proto__ property. To check for null in this case, you can use the hasOwnProperty() method to determine if __proto__ exists. For example:

<code class="js">if (!(newtoy.hasOwnProperty("__proto__"))) {
  // `__proto__` is not supported
}</code>

Visual Representation

To aid in理解ing, here's a visual map of the prototype chain and the relationship between __proto__ and constructor.prototype:

[Image of prototype chain and __proto__/constructor.prototype relationships]

This simplified diagram gives a comprehensive overview of the inner workings of JavaScript objects, helping clarify the distinction between these properties and their role in the prototype chain.

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