练习16
1.选择题
(1) C (2) A (3) A (4) D (5) A (6) A (7) A (8) C (9) A (10) D (11) C
2.填空题
(1)length
(2)random()、PI
(3)true、false
(4)文档对象模型(Document Object Model)、元素节点、文本节点、属性节点
(5)getElementById()、getElementsByName()、getElementsByTagName()
(6) createElement()、removeChild()、appendChild()
(7) innerText()、innerHTML()
(8) window、history、location、screen、navigator, window
(9) confirm()、alert()、prompt()
(10) navigator
3.问答题
见教材。
实验16
<!-- exp_16_1.html -->
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>猜字游戏</title>
<script type="text/javascript">
var win_rate=0; //赢率
var play_times=0; //总次数
var wins=0; //赢的次数
var last_digits; //上次数字串
var last_win; //上次是否赢?
function playOnce()
{//模拟玩一次数字机游戏
var i,digit;
play_times++;
last_digits="";
last_win=false;
for(i=0;i<3;i++)
{
digit = Math.floor(Math.random()*9)+1;
last_digits += digit;
if (digit==8)
last_win=true;
}
if(last_win)
wins++;
win_rate = Math.floor(100*(wins/play_times));
}
</script>
</head>
<body>
<script language="javascript">
while(true)
{
playOnce();
if (!confirm(last_digits +"\n" +(last_win?"赢":"输") + "\n您累计玩了"+play_times+"次,赢了"+wins+"次,胜率"+win_rate+"%,继续吗?" )) break;
}
</script>
</body>
</html>
2.代码 exp_16_2演示
<!-- exp_16_2.html -->
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>随机产生20个4位整数并从小到大进行排序</title>
<script type="text/javascript">
var numlist=new Array();//定义存放整数的数组
function $(id){return document.getElementById(id);}
function createNum(){
for (var i=0;i<20 ;i++ )
{
numlist[i]=Math.floor(Math.random()*9000+1000);
}
$("display").value="随机产生20个4位整数,分别如下:"+"\n"+numlist.join(",");
$("display").value=$("display").value+"\n从小到大排序后结果为:\n"+numlist.sort();
}
function findNum(){
var find_5time=new Array();
var i=0,j=0;
while (i<numlist.length)
{
if (numlist[i]%5==0)
{
find_5time[j]=numlist[i];
j++;
}
i++;
}
$("display").value+="\n能被5整除的整数有:\n"+find_5time.join(",");
}
</script>
</head>
<body>
<form method="post" action="">
<textarea id="display" name="" rows="10" cols="50"></textarea>
<br><br>
<input type="button" value="随机产生20个整数" onclick="createNum();">
<input type="button" value="找出能被5整除的整数" onclick="findNum();">
<input type="reset"></form>
</body>
</html>