求最大值、最小值
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>求最大值、最小值</title>
</head>
<body>
<script type="text/javascript">
var arr=[4,-20,3,8,34,5,49]
var max=arr[0]
for(var i=1;i<arr.length;i++){
if(max<arr[i])
max=arr[i]
}
document.write("最大值是:"+max)
document.write("<br />")
var min=arr[0]
for(var i=1;i<arr.length;i++){
if(min>arr[i])
min=arr[i]
}
document.write("最小值是:"+min)
</script>
</body>
</html>
for...in实现最大、小值
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>for...in实现最大、小值</title>
</head>
<body>
<script type="text/javascript">
var arr=[4,-20,3,8,34,5,49]
var max=arr[0]
var min=arr[0]
for(var i in arr){
if(max<arr[i]){
max=arr[i]
}
if(min>arr[i]){
min=arr[i]
}
}
document.write("最大值是:"+max)
document.write("<br />")
document.write("最小值是:"+min)
</script>
</body>
</html>
随机四位验证码
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>随机四位验证码</title>
<style type="text/css">
div{
border: 1px solid black;
width: 80px;
height: 30px;
}
</style>
</head>
<body>
<div id="dv"></div>
<button>注册</button>
<script>
var btn=document.querySelector('button')
btn.onclick=function(){
// 1.62个字符存放在数组中
let zi=[0,1,2,3,4,5,6,7,8,9,"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
// 2.取4次:0-61之间任意整数然后获取下标对应的字符
var s=''
for(var i=0;i<4;i++){
//0-61任意整数
var n=Math.random()*62
n=Math.floor(n)
s=s+zi[n]
}
// 3.放在div中
document.querySelector("#dv").innerHTML=s
}
</script>
</body>
</html>
增删改查
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>增删改查</title>
</head>
<body>
<script type="text/javascript">
var arr=new Array(10,20,30,40)
document.write(arr+"<br />")
//增加数组元素
arr[4]=50
arr[7]=80
document.write(arr+"<br />")
document.write(arr.length+"<br />")
//修改数组元素
arr[3]='hello'
document.write(arr+"<br />")
//清空整个数组
arr.length=0
document.write(arr+"<br />")
</script>
</body>
</html>
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