Technical

In this exercise you will create a NoSQL Document-Store database on Google Firebase and manipulate it by using a client-side data-grid component, part of the Shield UI JavaScript library.

In this article, we will demonstrate how to use the Shield UI Draggable component for changing the order of table rows by dragging them with the mouse.

Functions in JavaScript are objects. As objects, functions possess methods, including the powerful Bind method. Bind is used for setting the this value in methods, borrowing methods of other objects and for currying functions. Bind method is primarily used to call a function with the this value set explicitly. It enables us to easily set which specific object will be bound to this when a function is invoked.

Smart-designed code is much easier to maintain, optimize, and extend. There are three high-level aspects to code design that are particularly important.

- System architecture — the basic layout of the codebase. Rules that govern how various components, such as models, views, and controllers, interact with each other.
- Maintainability — how code can be improved and extended
- Reusability — how reusable are the application’s components and how easily can each implementation of a component be customized

Closures allow JavaScript programmers to write better and concise code. A closure is an inner function that has access to the outer (enclosing) function’s variables—scope chain. The closure has three scope chains: it has access to its own scope (variables defined between its curly brackets), it has access to the outer function’s variables, and it has access to the global variables. The inner function has access not only to the outer function’s variables, but also to the outer function’s parameters.

In JavaScript, functions are objects; that is, functions are of the type Object and they can be used in a manner like any other object since they are in fact objects themselves. They can be stored in variables, passed as arguments to functions, created within functions, and returned from functions. Because functions are objects, we can pass a function as an argument in another function and later execute that passed-in function or even return it to be executed later. This is the essence of using callback functions in JavaScript.

Iterators in C# are a very complex syntactic sugar. They take a function with yield return statements (and possible some yield break statements) and transfer it into a state machine. When you yield return, the state of the function is recorded, and execution resumes from that state the next time the iterator is called upon to produce another object. The local variables of the iterator, including the hidden this parameter, become member variables of a helper class.

The HTML5 standard has introduced a lot of new features to establish the basis for modern web. It has learned from the offerings of existing browsers and incorporated modern features. Web pages like blog postings and rich comment boxes require users to decorate their text to emphasis key points and this requires the ability to expose users to define their input in HTML form. Internet Explorer 5 had introduced a couple of attributes to help with HTML editing – contenteditable and designMode.

The Adapter design pattern converts a class interface into another one the client expects. This pattern lets classes work together otherwise they couldn't because their interfaces are incompatible. The essence of the pattern is transferring an interface (object's properties and methods) to another. A common scenario of the pattern use is when new components and modules need to be integrated to work with existing ones in an application or when part of code is refactored with improved interface but still needs to work with old parts.

The Visitor pattern defines a new operation or a set of operations on an object or a set of objects without changing the objects themselves. The new logic is implemented in a separate object defined as visitor. That is useful when building extensibility in a library or a framework. If objects provide a visit method accepting the visitor object making alterations to the current one, then there is a flawless way for clients to implement future extensions.