Should we define all public methods or prototype each method separately?

Question

Should we define all public methods or prototype each method separately?

Typically, when I create a library, my approach is as follows:

var myLibrary = (function() {
    return {
        publicProperty: 'test',
        publicMethod: function() {
            console.log('public function');
        },
        anotherMethod: function() { //... },
        // .. many more public methods
    };
}());

I recently heard that there may be a difference in speed or memory usage during initialization if the library is written like this:

var MyLibrary = function() {
   this.publicProperty = 'test';
};

MyLibrary.prototype = {
    publicMethod: function() {
        console.log('public method');
    },
    anotherMethod: function() { //... },
    // ... many more public methods
};

myLibrary = new MyLibrary();

Is one of these methods faster to initialize than the other? Does my question even make sense? I assume both achieve the same goal (whereby I can use myLibrary.publicMethod() elsewhere in my code after document readiness). Thank you!

javascript initialization libraries prototype-programming public-method

Answer 1

Answer №1

The outcomes of the two scripts vary.

In the initial script, you establish the object myLib with three (or more) attributes. It inherits from Object.prototype, essentially creating a single object.

On the other hand, in the second script, you introduce a global variable named publicProperty, which may not align with your intended outcome. (EDIT: OP Question Corrected, this is no longer an issue.)

If your aim was to produce an object with methods within the prototype, your code might perform slower on a simple JavaScript engine because calling methods in the prototype necessitates traversing the connection from the object to the prototype.

However, if your objective is to generate multiple instances of myLib, storing methods in the prototype can conserve memory by having only one instance of each function. Having numerous duplicates of methods is inefficient and resource-heavy. :)

EDIT TO ADDRESS OP QUESTION:

In consideration of the two techniques and how to enhance the speed of the first approach:

There's a potential tradeoff between space and time. Placing the methods directly in the object eliminates the need for prototype chain lookup. Yet, each instance will have its own set of methods, leading to duplication. If you plan to create multiple instances, it's preferable to define the methods once and assign them to a prototype. Modern JavaScript engines like V8 handle this optimization well, so packing methods into the object solely for speed improvement isn't necessary. However, for singletons, loading up the object could be beneficial. Another strategy involves enclosing all the methods within myLib itself and generating instances using Object.create(myLib). This way, myLib becomes the prototype for all "instances," following the principles outlined in "Good Parts".

Answer 2

The outcomes of the two scripts vary.

In the initial script, you establish the object myLib with three (or more) attributes. It inherits from Object.prototype, essentially creating a single object.

On the other hand, in the second script, you introduce a global variable named publicProperty, which may not align with your intended outcome. (EDIT: OP Question Corrected, this is no longer an issue.)

If your aim was to produce an object with methods within the prototype, your code might perform slower on a simple JavaScript engine because calling methods in the prototype necessitates traversing the connection from the object to the prototype.

However, if your objective is to generate multiple instances of myLib, storing methods in the prototype can conserve memory by having only one instance of each function. Having numerous duplicates of methods is inefficient and resource-heavy. :)

EDIT TO ADDRESS OP QUESTION:

In consideration of the two techniques and how to enhance the speed of the first approach:

There's a potential tradeoff between space and time. Placing the methods directly in the object eliminates the need for prototype chain lookup. Yet, each instance will have its own set of methods, leading to duplication. If you plan to create multiple instances, it's preferable to define the methods once and assign them to a prototype. Modern JavaScript engines like V8 handle this optimization well, so packing methods into the object solely for speed improvement isn't necessary. However, for singletons, loading up the object could be beneficial. Another strategy involves enclosing all the methods within myLib itself and generating instances using Object.create(myLib). This way, myLib becomes the prototype for all "instances," following the principles outlined in "Good Parts".

Answer 3

Answer №2

Update: After reviewing the modifications made to the question, I pose this query to you:

Are you considering having multiple "instances" of your library running concurrently?

If not, there doesn't appear to be any advantage in utilizing a constructor. You will only have one object, so defining properties on its prototype seems unnecessary - they will all be utilized within a single object anyway.

Employing inheritance would be beneficial if you intend to have multiple object instances where the methods are shared and declared just once higher up in the prototype chain for reuse.

There are several issues present in your second example:

var myLib = (function() {
   this.publicProperty = 'this';
}());

The variable myLib will simply hold undefined since nothing is being returned from the function expression. Additionally, your publicProperty will be defined as a property of the global object because of how the function is executed, with this associated with the global object.

If the code runs under strict mode, the this value will be

undefined</code, leading your property access expression to throw a <code>TypeError

. This can actually be beneficial to prevent inadvertently declaring publicProperty as a member of the global object.

myLib.prototype = {
    publicMethod: function() {
        console.log('public method');
    },
    anotherMethod: function() { //... },
    // ... many more public methods
};

Accessing the prototype property here will fail since remember, myLib is undefined.

The prototype is significant for functions used in constructor functions intended for use with the new operator. It appears there may be confusion with that property and the internal [[Prototype]] property that all objects possess.

Assigning a property named prototype to a non-function object will have no impact.

For further information, refer to:

JavaScript prototype limited to functions ??

Answer 4

Update: After reviewing the modifications made to the question, I pose this query to you:

Are you considering having multiple "instances" of your library running concurrently?

If not, there doesn't appear to be any advantage in utilizing a constructor. You will only have one object, so defining properties on its prototype seems unnecessary - they will all be utilized within a single object anyway.

Employing inheritance would be beneficial if you intend to have multiple object instances where the methods are shared and declared just once higher up in the prototype chain for reuse.

There are several issues present in your second example:

var myLib = (function() {
   this.publicProperty = 'this';
}());

The variable myLib will simply hold undefined since nothing is being returned from the function expression. Additionally, your publicProperty will be defined as a property of the global object because of how the function is executed, with this associated with the global object.

If the code runs under strict mode, the this value will be

undefined</code, leading your property access expression to throw a <code>TypeError

. This can actually be beneficial to prevent inadvertently declaring publicProperty as a member of the global object.

myLib.prototype = {
    publicMethod: function() {
        console.log('public method');
    },
    anotherMethod: function() { //... },
    // ... many more public methods
};

Accessing the prototype property here will fail since remember, myLib is undefined.

The prototype is significant for functions used in constructor functions intended for use with the new operator. It appears there may be confusion with that property and the internal [[Prototype]] property that all objects possess.

Assigning a property named prototype to a non-function object will have no impact.

For further information, refer to:

JavaScript prototype limited to functions ??

Should we define all public methods or prototype each method separately?

Answer №1

Answer №2

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