javascript - 如何将 JavaScript 回调设置为外部(包装)对象的方法？

Question

如何将 websocket 属性 onopen 回调委托(delegate)给外部对象的方法 with outer-object as this, not websocket as 这个？ (因为 websocket 没有函数 showAlert

换句话说:如何在 webscoket connect 上调用我的 MyClient.showConnected？

function MyClient() {
    this.websocket = {};
}

MyClient.prototype.showAlert = function( ) {
    alert("Connected!");
};

MyClient.prototype.showConnected = function( evt ) {
    this.showAlert();
};

MyClient.prototype.connect = function( url ) {
    this.websocket = new WebSocket(url);
    this.websocket.onopen =  this.showConnected;
}

这种方式产生this.showAlert is not a function。用法:

var client = new MyClient();
client.connect("ws://.......");

这也不工作:

this.websocket.onopen = function(evt) { this.onOpen(evt); };

Answer 1

function MyClient() {
    this.websocket = {};
}

MyClient.prototype.showAlert = function( ) {
    alert("Connected!");
};

MyClient.prototype.connect = function( url ) {
    this.websocket = new WebSocket(url);
    this.websocket.onopen = this.showAlert.bind(this);
}