Utility classes

Apart from ready-to-go components, Bootstrap offers a large selection of utility classes that encapsulate the most commonly needed functionality in order to reduce the number of repetitive style rules. Examples of such utilities include classes for quickly styling borders, clearing floats, creating generic close icons, defining colors, changing the display and visibility properties of elements, and adjusting size and spacing. Some of these utility classes already existed in Bootstrap 3, while others are brand new or have been adapted, renamed, or modified. We will be using these utility classes throughout the course of this book, and they will gain our full, undivided attention in Chapter 8, Utilities, for example, rules for aligning text, hiding an element, or providing contextual colors for warning text.