Tham khảo sách 'javascript bible_ chapter 6', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Programming Fundamentals Part I The tutorial breaks away from HTML and documents for a while as you begin to learn programming fundamentals that apply to practically every scripting and programming language you will encounter. You ll start here learning about variables expressions data types and operators things that might sound scary if you haven t programmed before. Don t worry. With a little practice you will become quite comfortable with these terms and concepts. Working with Information With rare exception every JavaScript statement you write does something with a hunk of information data. The chunk of data may be text information displayed on the screen by a JavaScript statement or the on off setting of a radio button in a form. Each single piece of information in programming is also called a value. Outside of programming the term value usually connotes a number of some kind in the programming world however the term is not as restrictive. A string of letters is a value. A number is a value. The setting of a checkbox the fact of whether it is checked or not is a value. In JavaScript a value can be one of several types. Table 6-1 lists JavaScript s formal data types with examples of the values you will see displayed from time to time. A language that contains these few data types simplifies programming tasks especially those involving what other languages consider to be incompatible types of numbers integers versus real or floating-point values . In some definitions of syntax and parts of objects later in this book I make specific reference to the type of value accepted in placeholders. When a string is required any text inside a set of quotes suffices. In This Chapter What variables are and how to use them How to evaluate expressions How to convert data from one type to another How to use basic operators 62 Part II JavaScript Tutorial Table 6-1 JavaScript Value Data Types Type Example Description String Howdy A series of characters inside quote marks Number .
