<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script>
var oddSum = function(n,fn){
var sum = 0
fn = fn || function(n){
return n
}
for(var i=0i<ni++){
if((i+1)&1==1){
for(var j=0j<i+1j++){
if((j+1)&1==1)
sum+=fn(j+1)
}
}
}
return sum
}
var factorial = function(n){
return n>1 ? n*factorial(n-1) :1
}
document.write('S=1+(1+3)+(1+3+5)+…+(1+3+5+…+19)'+oddSum(19))
document.write('<br>')
document.write('S=1!+ (1!+3! )+(1!+3!+5!)+…+(1!+3!+5!+…+19!)'+oddSum(19,function(n){ return factorial(n) }))
</script>
</head>
<body>
</body>
</html>
<!doctype html><html>
<head>
<title>计算器</title>
<meta charset="utf-8"/>
<style type="text/css">
.panel{
border:4px solid #ddd
width:192px
margin:100px auto
}
.panel p,.panel input{
font-family:"微软雅黑"
font-size:20px
margin:4px
float:left
}
.panel p{
width:122px
height:26px
border:1px solid #ddd
padding:6px
overflow:hidden
}
.panel input{
width:40px
height:40px
border:1px solid #ddd
}
</style>
<script type="text/javascript">
//参数e用来接收传入的event对象
function cal(e){
//1.获取事件源，处理button的事件
var obj=e.srcElement||e.target
if(obj.nodeName !="INPUT"){
return
}
var value=obj.value
var p=document.getElementById("screen")
if(value=="C"){
//2.如果是[C]，则清空p
p.innerText=""
}else if(value=="="){
//3.如果是[=]，则运算
var exp=p.innerText
try{
var result=eval("("+exp+")")
//如果正确执行，将结果写入p
p.innerText=result
}catch(e){
//发生错误，给予错误提示
p.innerText="Error."
}
}else{
//4.如果是其它按钮，则将value追加到p中
p.innerText+=value
}
}
</script>
</head>
<body>
<!--在最外层的div上注册单击事件，传入event对象，然后在函数中通过event判断出事件来源于哪一个button，
进而做出应有的处理。这样的好处是，避免在button上大量的注册事件。-->
<div class="panel" onClick="cal(event)">
<div>
<p id="screen"></p>
<input type="button" value="C">
<div style="clear:both"></div>
</div>
<div>
<input type="button" value="7">
<input type="button" value="8">
<input type="button" value="9">
<input type="button" value="/">
<input type="button" value="4">
<input type="button" value="5">
<input type="button" value="6">
<input type="button" value="*">
<input type="button" value="1">
<input type="button" value="2">
<input type="button" value="3">
<input type="button" value="-">
<input type="button" value="0">
<input type="button" value=".">
<input type="button" value="=">
<input type="button" value="+">
<div style="clear:both"></div>
</div>
</body>
</html>
这是我自学时候写的计算器
