Objects in JavaScript: properties, methods, and prototypes

This article provides a comprehensive understanding of JavaScript objects, going in-depth about properties, methods and prototypes. It also…

Anton Ioffe · 11 minute read


Welcome to the detailed exploration of JavaScript objects, properties, methods, and prototypes – the essence of JavaScript programming. Understanding these plays a significant part in leveraging the versatility and scalability of JavaScript, transforming these bridges of knowledge into powerhouse tools for creating flexible code. Picture JavaScript objects as elaborate data storage containers, properties as defining elements, methods as functionalities, and prototypes as the backbone of the object-oriented structure of JavaScript.

JavaScript objects are complex structures that house data in terms of properties. They are capable of storing several differing values, unlike primitive data types like numbers or strings. We can visualize these as multi-compartment storage containers for data. Further, these objects house various functionalities, known as methods, acting as verbs offering dynamic abilities within these JavaScript objects.

If objects are the vessels holding the values and methods act as the functionality within, properties are the distinctive attributes. Simply put, properties attached to an object serve to define its unique characteristics. For example, if we have an object representing a car, properties could be the brand, model, color, and so on.

Yet, it is prototypes that form the crux of JavaScript's object-oriented programming. By enabling properties and methods to be shared across multiple instances, prototypes foster code reusability and optimization. Prototypes function as blueprint systems, serving as templates that guide object creation within JavaScript.

Consider these examples for a rudimentary understanding:

Example 1: Creating a JavaScript object

var car = {brand: "Toyota", model: "Corolla", year: 2021};

In this, "car" is an object with properties: brand, model, and year.

Example 2: Incorporating a function (method)

car.start = function () {return "Engine Started";};

We just integrated a method, "start," within our "car" object. This method, when invoked, will return the string "Engine Started".

However, despite their core advantages, these elements can also create room for confusion, resulting in common coding errors, such as:

Common Mistake 1: Assigning properties outside the object

car.color = "blue";

This is erroneous because the property (color) was not initially encapsulated within the object's definition.

It provokes thought—what is your understanding of JavaScript objects, properties, methods, and prototypes? The degree of your understanding will shape your problem-solving skills and expertise in JavaScript programming.

However, bear in mind, this section only acts as an introduction, merely skimming the surface of these deep concepts. Subsequent sections will delve more profoundly into these concepts' depths. We've only just begun to explore the compelling realm of JavaScript objects, properties, methods, and prototypes. The detailed exploration awaits you in the subsequent stages of the journey through JavaScript.

Structuring JavaScript Objects

Programming with JavaScript involves a crucial understanding of the structure of JavaScript objects. These objects are essential as they can hold many values as properties. Essentially, JavaScript objects are like packaged bundles of code, serving as variable containers that can encompass variables and functions. The incorporated variables are recognized as the object's properties.

Creating JavaScript objects can be achieved in various ways, one of which is using an object literal, a method prevalently used in JavaScript due to its easy notation for new objects. This entails defining an object and its properties using a comma-separated list of property-value pairs enclosed in curly braces. Take for example:

let student = {
   name: "John",
   age: 22,
   isGraduated: false

In this example, student is the JavaScript object featuring three properties: name, age, and isGraduated. Each pair consists of a key and a value. There can be different types of properties including strings, as in name, numbers, like age, booleans, for instance, isGraduated, along with objects and functions.

It’s commonplace for developers to face challenges when working with JavaScript objects, chiefly owing to the incorrect use of the 'this' keyword and inappropriate setting of object properties. In JavaScript, the 'this' keyword represents the object itself, with its value reliant on its usage. Contrary to what one might think, 'this' in an object method does not refer to the method, but to the object it belongs to. The main confusion occurs when a developer tries to access properties through 'this' in a nested function, as in this case, 'this' will point to the global object, and not the desired properties.

Setting properties correctly on an object also poses issues commonly seen in programming. Despite JavaScript allowing new properties to be added to existing objects, if an attempt to set a non-existent property is made, JavaScript will create a new property within that object—this may not always be the intended outcome.

With this knowledge, it will be valuable to consider questions like: What variety of property types can you include in a JavaScript object? How does the structure of a JavaScript object impact its functionality in coding? A solid understanding of JavaScript objects’ structure and property types gives you greater control over your programming approach.

Unraveling the essence of JavaScript objects and their properties can lead to a better appreciation of the dynamic environment of JavaScript, filled with multipurpose objects, each designed to fulfill different roles in your web application. Mastering these concepts while navigating through common errors can polish you into a more proficient JavaScript developer.

Breaking Down JavaScript Object Methods

In exploring the complexity of JavaScript, objects stand out as key players. JavaScript object methods, a fundamental aspect of these objects, lean into the language's inherent dynamism. Essentially, these object methods are actions we perform on objects. They are stored as function properties within the object, serving an efficient data manipulation and organization function.

Consider this example:

let myObject = {
  property1: 'Hello',
  functionProperty1: function() {

Above,'functionProperty1' serves as an object method for the 'myObject' object and is invoked like so:

myObject.functionProperty1(); //logs 'Hello'

The ‘this’ keyword can be perplexing, particularly for beginners. In JavaScript, 'this’ pertains to the object it belongs to. When used in an object method, 'this' is referring to the object which owns the method. However, outside of this context, 'this' refers to the global object.

A common pitfall is the confusion between JavaScript functions and methods. Remember, although both functions and methods can behave similarly, their invocation differs. Functions are invoked with arguments, whilst methods are invoked on an object, thereby accessing the object’s variables and properties.

This raises some fundamental questions to ponder: What distinguishes methods from functions in JavaScript? When is it more beneficial to use JavaScript object methods rather than functions? The answers hinge on the specific context of your code - and your programming aims.

So, when the context calls for JavaScript, grasp the nuances between object methods and functions. Harness both appropriately to elevate the efficiency of your code. Guard against misunderstandings around the 'this' keyword. Embrace JavaScript's unique structure where methods and functions can exist as properties for better code efficiency.

The Prototype Principle in JavaScript

JavaScript prototypes serve as a fundamental component of object-oriented programming within JavaScript, playing an essential role in inheritance mechanisms. Using prototypes, developers can determine which object is intended to act as a template—or prototype—for other objects to inherit structure and methods.

Consider this practical example. In JavaScript, when you want to create multiple objects possessing identical properties or methods, constructor functions are commonly used. For instance:

function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;

var myCar = new Car('Toyota', 'Corolla', 2005);

In this piece of code, Car is a constructor function. A new car object, myCar, can be created using the 'new' keyword. This process is tightly related to JavaScript's prototype inheritance since every JavaScript object possesses a prototype from which it can inherit properties and methods.

However, care must be taken not to stumble over common errors while engaging with JavaScript prototypes, especially when omitting the 'new' keyword with constructor functions. For instance, if we call the Car constructor without using the 'new' keyword, the outcome varies drastically:

var myCar = Car('Toyota', 'Corolla', 2005);

In this scenario, myCar would be undefined. This is because, in the absence of the 'new' keyword, the 'this' keyword within the Car function refers to the global object, not a new Car object. Consequently, properties are generated on the global object, and the function will return undefined.

Misunderstanding around prototype chains is another common pitfall. A prototype chain is a method for one object to access another object's properties and methods. This can occur when an object's prototype also has a prototype. If a property or method is not discovered on an object, JavaScript will traverse this prototype chain until it finds what it needs or reaches the end of that chain.

In conclusion, prototypes provide a breadth of expression and versatility in JavaScript. So, let's ponder over these questions - how does prototyping elevate object-oriented programming in JavaScript? And, can a JavaScript object exist without a prototype? Exploring these themes will unveil the fascinating potentials that lie within this concept.

JavaScript Classes vs. Prototypes

The introduction of ES6 (ECMAScript 6) classes in JavaScript has notably streamlined object and constructor creation. But remember, ES6 classes in JavaScript are not fundamentally new, they are essentially a simplified syntax over the conventional prototype-based inheritance—merely a syntactic sugar coating, which can be more intuitive for many developers.

One common misconception among programmers coming from class-based languages to JavaScript, is that they view JavaScript too as a class-based language. In reality, JavaScript is a prototype-based language. The advent of ES6 classes can inadvertently mask this crucial concept, and hence it's critical to grasp how ES6 class and prototypes are analogous in order to fully leverage JavaScript.

Let's illustrate this equivalence with an example. Suppose we want to create a "Book" object, starting with the ES6 class syntax. We introduce a "Book" class, featuring a constructor and a "readBook" method:

class Book {
  constructor(title) {
    this.title = title;

  readBook() {
    return `Reading ${this.title}`;

let myBook = new Book("Great Expectations");

JavaScript interprets this class internally using prototypes as below:

function Book(title) {
  this.title = title;

Book.prototype.readBook = function() {
  return `Reading ${this.title}`;

let myBook = new Book("Great Expectations");

Both these methods are different avenues leading us to the same result: the creation of a constructor function, a method, and a novel object instance.

It is quite prevalent among developers to consider JavaScript classes and prototypes as unrelated entities, a misconception that misdirects them to believe that ES6 marked a transition from prototype-based to class-based inheritance. The reality is, while the class syntax eases and intuits the coding process, it neither supersedes nor sidelines prototypes.

Take a moment and ponder upon these questions - How different does creating an object using an ES6 class vs. a prototype seem to you? Which of these aligns more closely with your programming style and why? Reflecting upon these questions will clarify your preferred coding practices and help you in optimally harnessing JavaScript.

In conclusion, both ES6 classes and prototypes occupy a central place in the sphere of JavaScript programming. The former offers a more contoured method to define objects and constructors, whereas the latter is the very fabric of JavaScript. A deep understanding of both these concepts and their inter-relation remains a cornerstone to excel in JavaScript programming.

Always bear in mind that JavaScript is not a pure class-based language, which is apparent from the instrumental role prototypes play in it. While ES6 class syntax certainly makes code easier to read and write, grasping prototype-based inheritance, which effectively is the backbone of JavaScript, facilitates more dynamic and robust coding practices.

Decoding Prototype Methods

In JavaScript, prototype methods present intriguing use cases and potential pitfalls. Unpacking this feature helps grasp its functionalities and its differentiations from traditional object methods.

Prototype methods in JavaScript are shared methods that all instances of a particular model or object can access. However, a notable difference between them and object methods is that they do not exist within each individual object instance. Herein lies the fundamental distinction: prototype methods are communal, while object methods are unique.

Take for example a simple function named "Robot". This function may establish default properties for every robot, including elements such as "model", "manufacturer", and "charge_life". At this point, these properties would be exclusive to each robot instance. However, if we wanted to add a functionality that applies to all robots, e.g. "perform" – a function that articulates the tasks the robot can accomplish? A common error would be to add this feature directly to the Robot function, resulting in a unique perform method for every robot - impractical and memory-intensive.

A savvy developer adds this method to the Robot's prototype, thus creating a prototype method. Now, every instance derived from the "Robot" function can utilise the "perform" method without each instance housing a copy of this method, results in efficient memory use. To accomplish this, use the following format: Robot.prototype.perform = function() {...perform functionality...};. Every robot can now execute the perform method without it being a unique property.

The merits of prototype methods are apparent: resource economy. Managing large numbers of object instances while allocating memory for a homogenous function for each instance is resource-profligate. Shared prototype methods offset this by allowing each instance to access the same method instead creating a new version each time.

Therefore, an understanding of JavaScript prototype methods and their differentiation from object methods is beneficial for efficient code. However, the journey to mastering this concept is continuous, prompting exploratory questions: What additional benefits might prototype methods offer over object methods? How might the differences between the two be leveraged for more efficient code?

The realm of JavaScript is vast, and we've barely skimmed its surface. So keep nurturing your curiosity - avoid complacency and keep exploring. Remember, it's not about prototypes or objects themselves, but how you structure and deploy them, that makes your code great.

Wrapping Up the Woven Web: JavaScript Objects, Properties, Prototypes, Methods

We have delved into a comprehensive exploration of JavaScript objects, properties, prototypes, and methods in this article. Recognizing the interconnectedness of these key principles brings to light the power and flexibility of JavaScript's object-oriented approach.

To recap, let’s go back to our primary units, JavaScript objects. These are simple, modifiable structures packed with data that act as the foundation of most JavaScript programming. Their characteristics, or properties, can be defined to manipulate and access data in diverse ways.

Next, we brought up the topic of methods - nothing more than functions that are object's properties. These methods allow for further refinement and complexity as they can interact with the object's data.

Not to forget, we outlined JavaScript prototypes which enable us to conveniently define properties and methods to be shared across instances of an object. This approach empowers us to design a prototype or a template of an object and subsequently create numerous instances of that object with the prototype's characteristics.

Moreover, we lightly touched upon ES6 classes, an elegant representation over JavaScript's conventional prototype-based inheritance. This simple yet expressive coding language renders JavaScript more similar to the traditional object-oriented languages.

However, there is a prevalent misapprehension of considering JavaScript objects as rigid entities similar to conventional classes or records.

Unlike structured entities, JavaScript objects are highly adaptive - properties can be appended, altered, or removed at any stage. They aren't immutably predefined. Likewise, methods can also be added, reshaped, or eliminated on an as-needed basis.

Reflect on the following questions: Has your perception of JavaScript objects, properties, prototypes, and methods undergone any changes after reading this article? How could these principles, when effectively implemented, enhance your programming and debugging proficiency?

Regular re-examination of these concepts will help consolidate your understanding, considering their complexity.

With these core components of JavaScript under your belt, you’re well-positioned on your journey to master this dynamic language. Grasping JavaScript objects, properties, methods, and prototypes will empower you to crack more sophisticated coding challenges and build more dynamic, efficient web applications. Best of luck with your coding adventure!