如何在我的视图中显示Angular2异常

Question

Here my Javascript code that is written in Angular2. The issue is important but more important is: how can I print this error on Html page because this page is going to be displayed in a mobile web-view, so that developers from the other side can get the error. Even if JSON.stringify() is not work.

let webSocketURL =  "ws://localhost:7000";
message = '';
webSocket:any;
try {
    this.webSocket = new WebSocket(webSocketURL);

    this.webSocket.onopen = (openEvent)=>{
        this.message = "WebSocket OPEN";
        this.webSocket.send('hello from client');
    };
    this.webSocket.onclose =  (closeEvent) =>{
        console.log('closeEvent',closeEvent);
        this.message = "WebSocket CLOSE"+ JSON.stringify(closeEvent);
        alert("WebSocket CLOSE: " + JSON.stringify(closeEvent, null, 4));
    };
} catch (exception) {
    console.error(exception);
    this.message = " Got exception" + exception ;
}

My HTML code is as below

<p>
  This is stage 11 for socket demo and we are going to listion socket on ws://localhost:7000
</p>

<h3>Here is Message output ::{{message}} </h3>

My current output is as below:

What am I doing wrong?

Answer 1

If I get you correctly, you want to show the exception to other devs, if yes you can use this

let webSocketURL =  "ws://localhost:7000";
message : any;
webSocket:any;
try {
    this.message = null;

    this.webSocket = new WebSocket(webSocketURL);

    this.webSocket.onopen = (openEvent)=>{
       this.message = "WebSocket OPEN";
       this.webSocket.send('hello from client');
    };
    this.webSocket.onclose =  (closeEvent) =>{
        console.log('closeEvent',closeEvent);
        this.message = "WebSocket CLOSE"+ JSON.stringify(closeEvent);
        alert("WebSocket CLOSE: " + JSON.stringify(closeEvent, null, 4));
    };
} catch (exception) {
    console.error(exception);
    this.message = exception ;
}


<p>
  This is stage 11 for socket demo and we are going to listion socket on ws://localhost:7000
</p>

<h3 *ngIf="message">Here is Message output ::{{message | json}} </h3>

Pay attention I changed message type to any to have an object in there