Prototype vs. Constructor: Which Method Reigns Supreme for Defining Class Methods?

Advantages of Prototype vs Constructor Approach

When defining methods for a class, there are two common approaches: using the Constructor or Prototype. Both have their advantages and disadvantages.

Constructor Approach

The Constructor approach defines methods directly in the constructor function of the class:

var Class = function () {
    this.calc = function (a, b) {
        return a + b;
    };
};

Prototype Approach

The Prototype approach defines methods as properties of the class's prototype:

var Class = function () {};

Class.prototype.calc = function (a, b) {
    return a + b;
};

Advantages of Prototype Approach

• Universal Changeability: Methods defined via the prototype chain can be changed universally for all instances of the class. Changing the prototype method affects all existing instances.
• Performance: Prototype methods are created once and inherited by all instances, leading to better performance compared to constructor methods which are created each time the constructor runs.

Disadvantages of Prototype Approach

• Lack of Access to Private Variables: Prototype methods cannot access private variables defined in the constructor, limiting their usefulness in certain scenarios.

Function Literal vs Function Definition

The choice between function literals and function definitions is a matter of preference. Function literals hoist the function declaration to the top of the scope:

var Class = function () {};

Function definitions hoist the variable declaration, but not the assignment:

function Class () {};

The main difference arises when the function is called before it is assigned. Using a function literal, the function is available before the assignment, while using a function definition, it's not.

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