js 去掉以逗号分割的字符串中头尾和中间多余的逗号

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)