Is there a way to simulate a click on an alert in JavaScript?

StackOverflow https://stackoverflow.com/questions/563890

  •  05-09-2019
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Question

I have a page with an iframe whose source page is in a separate domain. From time to time, the source page generates an alert. When it does so, it stops what it is doing until the user clicks OK to the alert.

What I would like to do is programmatically click OK on this alert so the source page can get back to being useful. Is this possible?

Was it helpful?

Solution

JavaScript is single-threaded, which means when you call a function, it blocks until it returns. When you call alert(), that passes control to the browser which decides how to handle it. It is not Javascript which is popping the UI dialog, it is the browser. alert() does not return until the browser receives the "OK" event and returns control. The javascript thread is halted until that happens.

So for at least two different reasons stated in the above paragraph, the answer is no :)

OTHER TIPS

I'm pretty sure it's not possible.

You shouldn't have a problem if you know the text of the alert and don't mind getting dirty.

You can override the iframe window's alert with your own and do something to the effect of..

document.getElementById("InnerFrameName").contentWindow.alert = function(){
    if (arguments[0].toLowerCase() == "innerframe alert text")
        return; //supress
    else
        alert(arguments[0]);
};

Edit: I made a little test with a proxy handler (it's in asp.net/c# but you should get the idea)...

The external page in my test is a w3 page with a button that displays an alert, the alert is now passed through the user defined function.

I'm sure this is alot more dirty then you'd like to get.

Page:

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Hello From MyPage</title>
    <script type="text/javascript">
        function frameLoaded() {
            document.getElementById("InnerFrameName").contentWindow.alert = function() {
                if (arguments[0].toLowerCase() == "i am an alert box!!") {
                    alert("MESSAGES WOULD BE SUPRESSED: " + arguments[0]);
                    return; //supress
                } else {
                    alert(arguments[0]);
                }
            };
        }
        </script>
</head>
<body onload="alert('Hello from an unsupressed top level frame message!');">
    <form id="form1" runat="server">
            <div>
                <h1>Internal Page (Top Level)</h1>
                <hr />
                <iframe id="InnerFrameName" onload="frameLoaded();" src="PageProxy.ashx?externalURI=http://www.w3schools.com/JS/tryit_view.asp?filename=tryjs_alert"
                    style="width: 800px; height: 600px;">Derp!...</iframe>
            </div>
    </form>
</body>
</html>

Proxy Handler:

<%@ WebHandler Language="C#" Class="PageProxy" %>

using System;
using System.Web;

public class PageProxy : IHttpHandler {

    public void ProcessRequest (HttpContext context) {
            byte[] externalPage = new System.Net.WebClient().DownloadData(context.Request["externalURI"]);
            context.Response.OutputStream.Write(externalPage, 0, externalPage.Length);
            context.Response.End();
    }

    public bool IsReusable {
        get {
            return false;
        }
    }
}

What happens if you override alert with a no-op in your code?

e.g.

<script>
// uncomment next line to swallow alerts
//  function alert(nope) { return; }
<script>
<script>
  $(document).ready(function() { alert("Hello, world!"); });
</script>

With the line commented out, alert appears. With line commented in, alert does not appear.

I highly doubt it. If by separate domain, do you mean one which you have no control over?

If you do have control, you could change the alerts to modal Javascript boxes, which you could control.

The best bet to solve your problems with annoying JavaScript would be to override it with a client side scripting tool like Greasemonkey.

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