HTML and CSS Reference
In-Depth Information
EXPLANATION
3
Although we haven't formally covered
if
statements, we have used them in several
examples, and they should be easy to follow. (See Chapter 6, “Under Certain Con-
ditions,” for a formal introduction). If the value of
temp
is equal to
98.6
, then the
following block of statements will be executed.
4
If is the user entered 98.6, the alert box sends the message “
Your temp is normal
”
to the browser.
5
If line 3 is not true, the block of statements following
else
is executed. An alert box
will appear in the browser window saying, “
You are sick!
” (see Figure 5.26).
Figure 5.25
User enters a string. The
parseFloat()
function will convert it to a
floating-point number.
Figure 5.26
Output from Example 5.16.
The
eval()
function evaluates a string as a JavaScript expression, returning the result of
the execution.
3
If there is no result,
undefined
is returned.
FORMAT
eval(String);
EXAMPLE
eval("(5+4) / 3");
3. The
eval()
function takes a primitive string as its argument, not a
String
object. If a
String
object is used, it
will be returned as is.