The term "reactive programming" refers to a programming style based on handling "events" of all sorts. App developers are familiar with simple user interface events, such as mouse clicks, and know how to deal with them using their favorite programming language. But there are also other kinds of events an app may have to deal with, such as a state change of an object, an incoming message, the completion of an asynchronuous operation or an exception/error event.
Don't confuse a DOM collection with a JS array: Array functions, such as the forEach looping method, cannot be applied to a DOM collection!
For instance, when you retrieve all rows of an HTML table element, you get an HTMLCollection, which is an array-like object, but not an instance of Array, and therefore the following code does not succeed because the Array method forEach is not defined for an HTMLCollection like myTableEl.rows:
In the Web of Things (WoT), special communication networks composed of sensor nodes, actuator nodes and service nodes form the basis for new types of web applications, which are directly connected to the real world via sensors and actuators, and can be private, such as smart home apps, personal robotics apps and factory control applications, or public, such as air pollution monitoring systems and city parking management systems.
If you want to become a great app developer, it's not sufficient that you master your favorite programming technologies. It's essential that you understand all basic concepts and techniques, not just in programming, but also in information management.
The concept of a class is fundamental in object-oriented programming. Objects instantiate (or are classified by) a class. A class defines the properties and methods (as a blueprint) for the objects that instantiate it. Having a class concept is essential for being able to implement a data model in the form of model classes within a Model-View-Container (MVC) architecture.