let permission = ",,,106,105,108,,,109,110,107,,101,,," let permission = "106,105,108,109,110,107,101"
我们要把上面的字符串处理成想要的结果，最好的方法是使用正则，我的正则一直写不太好，就想换个思路解决。
首先想到个最笨的办法，先掐头去尾再解决中间的，但这也不是理解的办法，要写一大行代码，还容易 出错
就想到先把它转换成数组，再对数组去空，然后再转回字符串，完美解决
let permission = ",,,106,105,108,,,109,110,107,,101,,,"
console.log("permission",permission)
arry = permission.split(",");
console.log("arry",arry)
let arry2 =[]
arry.map((item)=>{
if (item !== "" && item != undefined) {
arry2.push(item);
}
})
arry2 = arry2.join(',')
console.log("arry2",arry2)