javascript - JavaScript で Library の EventHandler と "this" 修飾子を使用する

Question

ここでの例は、ブラウザで websocket を使用することです。WebsocketのwsライブラリでNodejsを使用した場合も同じことが起こりました。

クラスの外にすべてを書くと、すべてのハンドラが呼び出されます: EG:

try {
    var host = "ws://localhost:8080";
    var socket = new WebSocket(host); 

    socket.onopen = function(){ 
         // Do something
    } 
    socket.onmessage = function(msg){ // all stuff here will be called upon receiving message
         // Do something
    } 
    socket.onclose = function(){ 
         // Do something
    }            
} catch(exception){ 
     // Do something
}

ただし、クラスでインスタンス化する場合、ハンドラーは呼び出されません

var ws = new webSocketModule();

var webSocketModule = function(){
    try {
        var host = "ws://localhost:8080";
        this.socket = new WebSocket(host); 

        this.socket.onopen = function(){ 
             // Do something
        } 
        this.socket.onmessage = function(msg){ // None of these are called upon receiving message, however the server side will have connection message that means the websocket object is functioning just fine.
             // Do something
        } 
        this.socket.onclose = function(){ 
             // Do something
        }            
    } catch(exception){ 
         // Do something
    } 
}

それで、すべてをグローバルに配置するという厄介な方法でそれをしなければならないということですか?

質問に追加するには

var ws = new webSocketModule();

var webSocketModule = function(){
    try {
        var host = "ws://localhost:8080";
        this.socket = new WebSocket(host); 

        this.socket.onopen = function(){ 
             // Do something
        } 
        this.socket.onmessage = function(msg){
             // Do something
        } 
        this.socket.onclose = function(){ 
             // Do something
        }            
    } catch(exception){ 
         // Do something
    } 
}

ws.socket.onmessage = function(msg){
    // This will be called, kinda confusing
}

================================================== =============== 追加:

var ws = new webSocketModule();  //Explain: This is the instance in the main file

// Down below is in eg: webSocketModule.js
var webSocketModule = function(){
    try {
        var host = "ws://localhost:8080";
        var skt = this.socket = new WebSocket(host); 

        skt.onopen = function(){ 
             // Do something
        } 
        skt.onmessage = function(msg){
             // Using a local variable for socket will not make this respond
             // Another side will successfully show connected and send the message
             // (At least it successfully printed the console log after the socket.send)
             // You have to register it like the above block "ws.socket.onmessage = ..." in the main file to make it respond
             // But this and the object should be the same point of reference right?
             // Seems Javascript handles it differently than JAVA or C++, is there any book that recommended that talks about how browser or NodeJS handles it? thanks.
             // Do something
        } 
        skt.onclose = function(){ 
             // Do something
        }            
    } catch(exception){ 
         // Do something
    } 
}