Implementation method of obtaining specified cook information in js

function get_cookie(name)
    {
        var bikky = document.cookie;
        name += "=";
        var i = 0;
        while (i < bikky.length)
        {
            var offset = i + name.length;
            if (bikky.substring(i, offset) == name)
            {
                var endstr = bikky.indexOf(";", offset);
                if (endstr == -1) endstr = bikky.length;
                return unescape(bikky.substring(offset, endstr));
            }
            i = bikky.indexOf(" ", i) + 1;
            if (i == 0) break;
        }
        return null;
    }