條件敘述與迴圈
條件敘述
if/else 敘述區塊
if/else 敘述區塊結構
<SCRIPT language="JavaScript">
<!--
var boats=3;
if (boats==3)
{
window.alert("You have the right number of boats");
}
else
{
window.alert("You do not have the right number of boats");
}
//-->
</SCRIPT>
巢狀區塊
<SCRIPT language="JavaScript">
<!--
var have_cookbook="yes";
var meatloaf_recipe="yes";
if (have_cookbook=="yes")
{
if (meatloaf_recipe=="yes")
{
window.alert("Recipe found");
}
else
{
window.alert("Have the book, but no recipe");
}
}
else
{
window.alert("You need a cookbook");
}
//-->
</SCRIPT>
複雜的比較
<SCRIPT language="JavaScript">
<!--
var num1=9;
if ((num1>2)&&(num1<11)||(num1==20))
{
window.alert("Cool number");
}
else
{
window.alert("Not a cool number");
}
//-->
</SCRIPT>
switch 敘述
<SCRIPT language="JavaScript">
<!--
var name="Fred";
switch (name)
{
case "George" :
window.alert("George is an Ok name");
break;
case "Fred" :
window.alert("Fred is the coolest name");
window.alert("Hi there, Fred!");
break;
case default :
window.alert("Interesting name you have there");
}
//-->
</SCRIPT>
迴圈
for 敘述
for 迴圈結構
<html>
<head>
<title>Looping</title>
</head>
<body>
Get ready for some repeated text.
<SCRIPT language="JavaScript">
<!--
for (count=1;count<11;count+=1)
{
document.write("I am part of a loop!<br>");
}
//-->
</SCRIPT>
<p>
Now we are back to the plain HTML code.
</body>
</html>
巢狀區塊
<html>
<head>
<title>Nesting and Looping</title>
</head>
<body>
Get ready for some repeated text.
<SCRIPT language="JavaScript">
<!--
for (count=1;count<11;count+=1)
{
document.write(count+". I am part of a loop!<br>");
for (nestcount=1;nestcount<3;nestcount+=1)
{
document.write("I keep interrupting in pairs!<br>");
}
}
//-->
</SCRIPT>
<p>
Now we are back to the plain HTML code.
</body>
</html>
while 敘述
<html>
<head>
<title>Looping</title>
</head>
<body>
Get ready for some repeated text.
<SCRIPT language="JavaScript">
<!--
var count=1;
while (count<11)
{
document.write(count+". I am part of a loop!<br>");
count+=1;
}
//-->
</SCRIPT>
<p>
Now we are back to the plain HTML code.
</body>
</html>