有人可以向我解释while循环在javascript getCookie()中的功能吗?

很抱歉提出一个问题...以下是W3C学校的getCookie代码教程

sorry for a question to ask... Below is the tutorial of getCookie code from W3C School

有人会教我 while(c.charAt(0)=='')c = c.substring(1); 的作用是什么，既然是while循环，为什么会不会一直重复并卡在那儿?

Would someone teach me what is the function of while (c.charAt(0)==' ') c = c.substring(1); , and since it is while loop, why won't it keep repeating and stuck there?

谢谢...

function getCookie(cname) {
    var name = cname + "=";
    var ca = document.cookie.split(';');
    for(var i=0; i<ca.length; i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') c = c.substring(1);
        if (c.indexOf(name) == 0) return c.substring(name.length, c.length);
    }
    return "";
    }

   }