Differentiating proto and Constructor.prototype: What\'s the Key Distinction?

Understanding the Differences Between proto and Constructor.prototype

The proto property and the constructor.prototype are closely related concepts in JavaScript that frequently lead to confusion. This article aims to clarify their distinctions.

__proto__:

proto is an internal property of JavaScript objects that points to their prototype object. The prototype object contains properties and methods inherited by instances of that object. Objects inherit their proto property from their constructor function.

In the example, newtoy.__proto__ returns the Gadget.prototype object, which contains the inherited rating property.

constructor.prototype:

The constructor.prototype property of a function references the prototype object of the function. When an object is created using the new keyword, its constructor function's prototype becomes the prototype of the new object.

In the example, newtoy.constructor.prototype returns the Gadget.prototype object, which has the inherited rating property.

Prototypal Chain:

Both proto and constructor.prototype participate in the prototypal chain, a mechanism in JavaScript that enables objects to inherit properties and methods from their prototype objects.

newtoy.__proto__.constructor.prototype.constructor.prototype.constructor.prototype returns the Gadget.prototype object, which inherits from Function.prototype and ultimately ends at Object.prototype.

Internet Explorer:

Internet Explorer does not have a proto property. To check for null in this context, it is possible to use the hasOwnProperty() method to determine if the object contains a specific property.

For example:

<code class="javascript">if (Object.hasOwnProperty("__proto__")) {
  // __proto__ property is available
} else {
  // __proto__ property is not available
}</code>

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