Writing object-oriented JavaScript code is essential for building complex and maintainable applications. One of the key features of object-oriented programming is the use of classes and objects. To write object-oriented JavaScript, you can start by defining a class using the class keyword. Inside the class, you can define properties and methods. For example, you can create a class called 'Car' with properties like 'make', 'model', and 'year', and methods like 'start' and 'stop'. Once you've defined a class, you can create objects based on that class using the new keyword. For instance, you can create a new instance of the 'Car' class and set its properties using dot notation. This allows you to create multiple objects with the same structure but different values. Additionally, you can use inheritance to create subclasses that inherit properties and methods from a parent class. This allows you to create a hierarchy of classes, making it easier to manage and reuse code. Overall, writing object-oriented JavaScript involves creating classes with properties and methods, creating objects based on those classes, and using inheritance to create a hierarchy of classes. By mastering these concepts, you can write clean, modular, and maintainable JavaScript code for your projects.