st=>start: 用户登陆
op=>operation: 登陆操作
cond=>condition: 登陆成功 Yes or No?
e=>end: 进入后台

st->op->cond
cond(yes)->e
cond(no)->op

                ### 绘制序列图 Sequence Diagram
                

Andrew->China: Says Hello 
Note right of China: China thinks\nabout it 
China-->Andrew: How are you? 
Andrew->>China: I am good thanks!

function test() {
    console.log("Hello world!");
}
 
(function(){
    var box = function() {
        return box.fn.init();
    };

    box.prototype = box.fn = {
        init : function(){
            console.log('box.init()');

            return this;
        },

        add : function(str) {
            alert("add", str);

            return this;
        },

        remove : function(str) {
            alert("remove", str);

            return this;
        }
    };
    
    box.fn.init.prototype = box.fn;
    
    window.box =box;
})();

var testBox = box();
testBox.add("jQuery").remove("jQuery");