Hide Javascript error message from browser

I found this code sample on one of the questions;

window.onerror = function (msg, url, linenumber) {  

 //make ajax call with all error details and log error directly into the elmah database

 //show friendly error msg here to user

 //hide error from browser
 return true; 
}

What does 'hide error from browser' means and how can I do that?

I didn't know such a thing exists and I give it a try with try-catch block. After an error occurred, I realized that browser still shows the error. How can I hide error from browser?

UPDATE

I tried following code and put that inside the head section of my all pages but noting happened;

<script type="text/javascript">

(function () {

    window.onerror = function myErrorHandler(errorMsg, url, lineNumber) {

  开发者_如何转开发      alert(errorMsg);

        // Just let default handler run.
        return true;
    }

})();

</script>

---

use: try...catch

function message()
{
    try
    {
        adddlert("Welcome guest!");
    }
    catch (err)
    {
        txt = "There was an error on this page.\n\n";
        txt += "Error description: " + err.description + "\n\n";
        txt += "Click OK to continue.\n\n";
        alert(txt);
    }
}

more: https://developer.mozilla.org/en/JavaScript/Reference/Statements/try...catch

---

When the function returns true, this prevents the firing of the default event handler.

It's just the way the browser behaves if this function returns true.

See more

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Adding window.onerror function to the head section and returning true would stop logging the errors events to the browser console.

As @Decko mentioned returning true prevents the firing of the default event handler.

Stackblitz - https://stackblitz.com/edit/web-platform-mfattr?file=index.html