CSS has dramatically changed since its very first emergence, and it is continuing to evolve. In particular, the emergence of CSS3 has added many new features to CSS, including gradients and animations. Along with this are many new opportunities to build websites using only CSS and HTML. Developers are no longer dependent on techniques such as Flash and other tricks to build interactive and fancy websites.
CSS3 has played an integral role in building responsive websites, where CSS media queries have made it possible to apply some styles dependent on the width of the browser's viewport only.
Despite this improvement, CSS is inherently, at its core, a simple style sheet language that lacks some fundamental programming features such as variables, functions, and operators. The need for more maintainable CSS, especially with the explosion of complex web apps, has made CSS preprocessors such as Less a necessity in enabling us to write more readable and manageable versions without breaking cross-browser compatibilities.
Although Less cannot magically change CSS, it certainly provides us with the tools to help structure, modularize, debug, and maintain small or large CSS projects more easily. By extending CSS with variables, functions, and mixins; nesting CSS selectors; and allowing you to follow the don't repeat yourself (DRY) principle of software programming, Less behaves more like a programming language in a way that CSS never was. Despite some of the programming characteristics of Less, you should not be put off by this; by being built as a superset of CSS, its features are implemented in the CSS way and it follows W3C standards where possible. Designers and developers who are familiar with CSS will find coding in Less very natural. Because Less fixes these shortcomings of CSS, the best time to start using Less is now!
In this book, you are going to explore the Less preprocessor, most of its core, and some of its less frequently used features. Through these very easy-to-follow and practical recipes, you will learn how to write more maintainable and scalable CSS. You will explore making components and structures through reusable mixins and extends. We will also learn about frameworks that are based on Less, exploring their features and how they can be seamlessly integrated into your own projects. In addition, you will learn how to use prebuilt mixin libraries for your current or upcoming projects. Finally, you will look at debugging techniques that have been available for other preprocessors and are now available to Less through source maps. By the end of this book, you will have an extended knowledge and a good understanding of the power of Less, its libraries, and the important features it has to offer to make writing your CSS more natural, productive, and intuitive.
Chapter 1, Getting to Grips with the Basics of Less, shows you how to install the Less compiler for client- and server-side usage. After the installation, you will be shown how to make use of the basic features of Less: using variables, mixins, operations, built-in functions, and namespaces; how to nest your rules will also be on the menu here!
Chapter 2, Debugging and Documenting Your Less Code, shows you how to debug your Less code using your CSS source maps and browser developer tools. You will also be introduced to style guides and learn how to properly comment your code.
Chapter 3, Using Variables and Mixins, covers the advanced usage of variables and mixins in Less. After reading this chapter, you will know how to use variables to create reusable Less code and use mixins to make your CSS properties interactive.
Chapter 4, Leveraging the Less Built-in Functions, explains the different types of built-in functions of Less. You will find examples of each type of function, including functions for color manipulation and mathematical operations.
Chapter 5, Extending and Referencing, shows you how to extend and reference selectors and properties to help you write better CSS and reduce the size of the compiled CSS code. You will learn to change the order of selectors and merge them.
Chapter 6, Advanced Less Coding, walks you through the process of parameterized mixins and shows you how to use guards. A guard can be used with as if-else statements and make it possible to construct interactive loops in Less.
Chapter 7, Leveraging Libraries with Prebuilt Mixins, explains how to install and use the libraries of prebuilt mixins. You will explore different libraries such as Less Elements, Less hats, and Preboot to build background gradients, grids, and animations in Less, among others.
Chapter 8, Building a Layout with Less, takes you through the process of creating a complete website layout with Less. The layout will be built with a responsive and semantic grid and will include a vertical menu. Finally, you will also learn how to use iconic fonts with Less.
Chapter 9, Using Bootstrap with Less, shows you how to customize Bootstrap and its components using Bootstrap's Less source files. You will also learn how to use Bootstrap's mixins to make semantic and reusable layouts and components.
Chapter 10, Less and WordPress, shows you how to use Less when theming your WordPress site. This includes examples of the Roots.io, SemanticUI, and JBST WordPress themes. You will be shown how to customize the WooCommerce plugins with Less along with integrating Less into your other WordPress themes and plugins.
Chapter 11, Compiling Less Real Time for Development Using Grunt, shows you how to set up a Less compiler using Grunt for real-time compilation. It will also show you how to use several Node modules for your Less development. By the end of this chapter, you will be very comfortable setting up a development environment with Grunt and its plugins.
The latest version of Less.js can be downloaded for free from http://www.lesscss.org/. You will definitely need a text editor to write your code; however, it does not matter which text editor or operating system you use. You will also need a modern web browser, namely the latest versions of Mozilla Firefox, Google Chrome, or Microsoft Internet Explorer. Please note that some recipes, especially in the final chapter, require some basic familiarity with the command line. All the tools used in the last chapter are cross-platform and are available for free, so you should be fine using your favorite operating system. Grunt plugins can be found by visiting http://gruntjs.com/plugins.
This book is mainly intended for web developers and designers who are comfortable with CSS and HTML. If you are someone with some experience with CSS, you will find the learning curve of understanding the Less syntax to be less steep. Although this book is beneficial to those who have had some experience with using Less, web developers and designers who would like to use this book as a gateway to learning the program can still benefit and harness its true power.
In this book, you will find several headings that appear frequently (Getting ready, How to do it, How it works, There's more, and See also).
To give clear instructions on how to complete a recipe, we use these sections as follows:
This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.
This section usually consists of a detailed explanation of what happened in the previous section.
This section consists of additional information about the recipe in order to make the reader more knowledgeable about the recipe.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "To start the process, you will have to edit your index.html file."
A block of code is set as follows:
header {
color: blue;
}
section {
color: green;
}
footer {
color: purple;
}When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
<link rel="stylesheet/less" type="text/css" href="less/styles.less" />
<script type="text/javascript">less = { env: 'development' };</script>
<script src="less.js" type="text/javascript"></script>Any command-line input or output is written as follows:
java -jar js.jar -f less-rhino-1.7.0.js lessc-rhino-1.7.0.js example.less example.css
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "In the Styles tab of the Developers Tools page, you will find the rules that are applied while selecting a selector."
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