Java Reference
In-Depth Information
Chapter 3
exercise 1 Question
A junior programmer comes to you with some code that appears not to work. Can you spot where
he went wrong? Give him a hand and correct the mistakes.
var userAge = prompt("Please enter your age");
if (userAge = 0) {;
alert("So you're a baby!");
} else if ( userAge < 0 | userAge > 200)
alert("I think you may be lying about your age");
else {
alert("That's a good age");
}
exercise 1 Solution
Oh dear, our junior programmer is having a bad day! There are two mistakes on the line:
if (userAge = 0) {;
First, he has only one equals sign instead of two in the
if
if's condition, which means
userAge
will be
assigned the value of
0
rather than
userAge
being compared to
0
. The second fault is the semicolon
at the end of the line—statements such as
if
and loops such as
for
and
while
don't require
semicolons. The general rule is that if the statement has an associated block (that is, code in curly
braces), no semicolon is needed. So the line should be:
if (userAge == 0) {
The next fault is with these lines:
else if ( userAge < 0 | userAge > 200)
alert("I think you may be lying about your age");
else {
The junior programmer's condition is asking if
userAge
is less than
0
OR
userAge
is greater than
200
. The correct operator for a boolean OR is
│
│
, but the programmer has only used one
|
.
exercise 2 Question
Using
document.write()
, write code that displays the results of the 12 times table. Its output should
be the results of the calculations.
12 * 1 = 12
12 * 2 = 24
12 * 3 = 36
...
12 * 11 = 132
12 * 12 = 144
