Summary

JavaScript programming is a problem-solving endeavor. It relies heavily on data and data expressions. At the start of this chapter, we mentioned that data could be people's names, temperature, image dimensions, the amount of disk storage, and total likes on a discussion group post. Data can be values for a user interface, such as screen coordinates, sizes, scroll values, colors, and fonts.

A JavaScript program is a series of steps that use data. A program starts with an event. An event could be when a web browser finishes loading the web page, a mouse event, such as a click or rolling over a spot on the screen, such as a button or image, or when some data is received from a web server that was requested by JavaScript.

Once the program begins, it executes the code statements sequentially and is directed by flow control statements such as if, switch, for, and while.

The code is organized into units called functions. Functions contain code that may need to be repeated in more than one part of a program, but with different data and different results. Functions can take data as input values and return a result; for example, Fahrenheit as input and Celsius as output.

JavaScript programs for web pages generally deal with the DOM. The DOM is just a large object that's created by the web browser. It is made up of all the data and functions

Before you try to solve every coding problem, you may find that other programmers have already solved many common problems and make their code available for you to use in the form of libraries and frameworks. For example, you could use JavaScript and the DOM to write code to animate user interface elements by sliding or fading them in and out of view. However, if someone has already solved that coding problem, you may want to use their code. In the next chapter, we will look at some popular libraries and frameworks that solve a wide range of problems for a web page.