Question

我正在创建一个类来回调Web套接字：

function QB() {
    var ws = null;

    this.connect = function () {
        // Let us open a web socket
        ws = new WebSocket("ws://localhost:9000/koule");

        ws.onopen = function () {
            if (this.onConnectionEstablished) {
                this.onConnectionEstablished();
            }
        };
        ws.onmessage = function (evt) {
            var msg = evt.data;
            //process callbacks
            parseMessage(msg);

        };
        ws.onclose = function () {
            if (this.onConnectionClosed) {
                this.onConnectionClosed();
            }
        };
        ws.onerror = function () {
            if (this.onConnectionError) {
                this.onConnectionError();
            }
        };
    };




    this.onConnectionEstablished = null;
    this.onConnectionClosed = null;
    this.onConnectionError = null;
}

然后我在这个样本中使用它：

<!DOCTYPE html>
<html>
    <head>
    <script type="text/javascript" src="qb.js"></script>
    </head>
    <body>

        <h1>My First JavaScript</h1>

        <p>Click Date to display current day, date, and time.</p>

        <button type="button" onclick="myFunction()">Date</button>

        <p id="demo"></p>

        <script>
            qb = new QB();


            qb.onConnectionEstablished = function()
            {
                alert('connected');
            };

        qb.onConnectionError = function()
        {
            alert('error');

        };

        qb.onConnectionClosed = function()
        {
            alert('closed');
        };


            function myFunction() {
                qb.connect();
            }
        </script>

    </body>
</html>

我没有得到任何警报，我应该至少得到其中一个。我在Chrome中检查了我的qb是否已正确创建，其ws变量将回调挂钩到它并且qb具有我设置的回调。

我无法弄清楚为什么这不起作用。

由于

Answer 1

匿名函数中的this范围不是QB实例的this：

ws.onopen = function () {
    if (this.onConnectionEstablished) {                  
         this.onConnectionEstablished()
    }
};

应该这样工作：

var self = this;
ws.onopen = function () {
    if (self.onConnectionEstablished) {                  
         self.onConnectionEstablished()
    }
};

我的课可能有什么问题？

1 个答案: