题目：
输入一个正整数n，生成n个随机密码，其中包括数字，大小写字母。
代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
div{
width: 300px;
height: 100px;
background-color: lightblue;
overflow: auto;
}
</style>
</head>
<body>
<input type="text">
<button>生成</button>
<div class="end"></div>
<script>
var oTn = document.getElementsByTagName("input")[0];
var oBtn = document.getElementsByTagName("button")[0];
var oDiv = document.querySelector(".end");
var password = ["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","0","1","2","3","4","5","6","7","8","9"
];
function pass(length){
var Str = "";
for(var i = 0 ; i<length;i++){
Str += password[Math.floor(Math.random()*password.length)];
}
return Str;
}
oBtn.onclick = function(){
oDiv.innerHTML = pass(oTn.value);
}
</script>
</body>
</html>
