Chapter 3. Decisions, Loops, and Functions
How will decision-making help you in creating web sites? In the last chapter you wrote some code that converted temperature in degrees Fahrenheit to centigrade. You obtained the degrees Fahrenheit from the user using the
prompt() function. This worked fine if the user entered a valid number, such as
50. If, however, the user entered something invalid for the Fahrenheit temperature, such as the string
aaa, you would find that your code no longer works as expected. Now, if you had some decision-making capabilities in your program, you could check to see if what the user has entered is valid. If it is, you can do the calculation, and if it isn't, you can tell the user why and ask him to enter a valid number.
Decision Making — The if and switch Statements
All programming languages enable you to make ...