Print javascript error in custom console

Question

I have a browser that doesn't have any console. I need to redirect the output to my home made console.

Is there a way to achieve that ?

Where does the home made console live?

Halcyon
– Halcyon

2015-02-10 14:00:50 +00:00
Commented Feb 10, 2015 at 14:00 — Halcyon
– Halcyon, Commented Feb 10, 2015 at 14:00
@Halcyon it's a fixed div into the webview

Dimitri Kopriwa
– Dimitri Kopriwa

2015-02-10 14:42:13 +00:00
Commented Feb 10, 2015 at 14:42 — Dimitri Kopriwa
– Dimitri Kopriwa, Commented Feb 10, 2015 at 14:42

T.J. Crowder · Accepted Answer · 2015-02-10 14:47:10Z

3

If it's just errors you want to catch, some of them will go to the window.onerror handler.

window.onerror = function(errorMsg, url, lineNumber) {
  // ...do something with the information...

  // Return false if you want to prevent the browser's default behavior
  return false;
};

edited Feb 10, 2015 at 14:47

answered Feb 10, 2015 at 14:03

T.J. Crowder

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4 Comments

Dimitri Kopriwa Over a year ago

Why "some of" ? I've checked you're link, have you tried that in production?

T.J. Crowder Over a year ago

@BigDong: That comment is based purely on the MDN page I linked; MDN is collaboratively-edited and therefore sometimes wrong, but usually right. I don't know in this case whether it is or not. I wondered if it might relate to code that couldn't even be parsed (e.g., in a separate script block), but in my tests of Chrome, Firefox, and IE11, all three called onerror even in that case.

Dimitri Kopriwa Over a year ago

I have tried on android browser, it didn't worked at all

T.J. Crowder Over a year ago

@BigDong: I can verify that on Android 2.3 (it doesn't work). My Android 4 devices are packed away at the moment, can't check them. Chrome for Android apparently works, but not the built-in browser. This page seems to have some info.

dfsq · Accepted Answer · 2015-02-10 14:17:22Z

You can create very simple custom "console" with few lines of HTML and javascript. For example:

var xConsole = {
    log: function(msg) {
        var output = '<div>' + msg + '</div>';
        document.getElementById('console').insertAdjacentHTML('beforeend', output);
    }
};

xConsole.log('test');
xConsole.log(new Date().getTime());

<pre id="console"></pre>

Then you will need to put this HTML line somewhere in the document (or append it dynamically). You could also use some CSS to style it or position it as you like.

UPD. Improved per comment by T.J. Crowder. Here is possible very basic solution that would also support error catching:

// uncomment below line and remove "if (true) {" when used in real world
//if (!window.console) {
if (true) {
    
    window.console = function() {
        
        var _ = {};
        
        _.log = function(msg) {
            var output = '<div>' + msg + '</div>';
            document.getElementById('console').insertAdjacentHTML('beforeend', output);
        };
        
        window.onerror = function(errorMsg) {
            _.log(errorMsg);
        };
        
        return _;
    }();
}

// Should log simple message
console.log('test message');

// Should log reference error
test + 1;

<pre id="console"></pre>

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