以@为间隔,每5个字符为间距,分隔字符串

var a = "1234567890111";
var b = "";
//从前往后数,每隔5个字符插入一个 @ 字符
for(var i = 0; i < a.length;i += 5){
b += a.substr(i,5)+"@";
}
//判断最后一个字符是否为 @ 字符
if(b.substr(b.length - 1 ,1) == "@"){
b = b.substr(0,b.length - 1)
}
console.log(b);

//从后往前数,每隔 5 个字符插入一个 @ 字符;
var a = "1234567890111";
var c = "",d = "",e = "";
//首先,把 a 的内容倒序赋值给 c;
for(var i = a.length - 1; i >= 0;i --){
c += a.substr(i,1);
}
//然后,给 c 的内容中插入 @ 字符并赋值给 d;
for(var i = 0; i < a.length;i += 5){
d += c.substr(i,5) + "@";
}
//最后, d 的内容倒序赋值给 e;
for(var i = d.length - 1; i >= 0;i --){
e += d.substr(i,1);
}
//判断第一个字符是否为 @ 字符
if(e.substr(0,1) == "@"){
e = e.substr(1,e.length - 1)
}
console.log(e)