JavaScript进行简单的随即验证码生成（适合和我一样刚入门一本完整的教材书都没看完的弟弟）

(感谢橙旭园给我打开了前端世界的大门)

var checkcode = document.getElementById("code");
var btn = document.getElementById("btn");
var refresh = document.getElementById("refresh");
var code = "";

//生成随机的验证码
function setCode(){
    code = "";
    var length = 4;
    var array = [0,1,2,3,4,5,6,7,8,9,'Q','W','E','R','T','Y','U','I','O',
'P','A','S','D','F','G','H','J','K','L','Z','X','C','V','B','N','M'];

for (var i = 0;i<length;i++){
    let index = Math.floor(Math.random() * 36);
    code += array[index];
    //Math.random()代表[0.0,1.0)这个区间的取值
    // Math.floor()代表获取整数值(math.floor()向下取整，.ceil()向上取整，.round()执行标准取整（四舍五入）)
    }
    checkcode.innerHTML = code;
}
setCode();
refresh.addEventListener("click",setCode,false);