js獲取指定的cookie

var cookieName = "cookie名字";
    var cookieValue = null;//返回cookie的value值
    if (document.cookie && document.cookie != '') {
        var cookies = document.cookie.split(';');//將獲得的所有cookie切割成數組
        for (var i = 0; i < cookies.length; i++) {
            var cookie = cookies[i];//得到某下標的cookies數組
            if (cookie.substring(0, cookieName.length + 2).trim() == cookieName.trim() + "=") {//如果存在該cookie的話就將cookie的值拿出來
                cookieValue = cookie.substring(cookieName.length + 2, cookie.length);
                break
            }
        }
    }
    if (cookieValue != "" && cookieValue != null) {//如果存在指定的cookie值
        alert(cookieValue);
    } else {//如果cookie的值是空
        alert("not cookie!!!");
    }

    //去除空格
    String.prototype.trim = function () {
        return this.replace(new RegExp("(^[\\s]*)|([\\s]*$)", "g"), "");
    }