Why is Firefox 3 breaking with console.log

Question

I have the following:

console.log (a.time_ago() + ' ' + b.time_ago());

This is breaking in FireFox 3, meaning when FF hits that line in the JS, it goes no further. Strangely if I have Firebug open it doesn't break and continues as normal. Some how firebug prevents this issue?

I'm puzzled on this one. Any thoughts as to why console.log would break firefox 3, but not if firebug is open?

Thanks

Hooky

Isn't console.log part of firebug? and hence if its not open, there's no container to paste to... – Zippy

Answer 1

This is not just Firefox. Your code will stop working in every browser (except Chrome and safari (in some instances) because they have console.log() built in along with their developer tools.)

It is because when you don't have firebug open, the object "console" is not defined. You should take care never too leave console.log() functions in your code, or it will break in every browser.

---

I'd like to add that I have sometimes used this function:

function log () {
    if (typeof console == 'undefined') {
        return;
    }
    console.log.apply(console, arguments);
}

Then you can simply call:

log(somevar, anothervar);

and it will work the same way as console.log, but will not fail if firebug is not loaded (and is shorter to type :P)

Cheers

Hypermetropia

You can use console.log(), just check if window.console exists before calling any console functions. E.g. if (window.console) console.log('Hello World'); – Brancusi

Thanks @generalhenry, I didn't know Safari also had it. That's helpful. – Hypermetropia

Firefox 4 will also have the console object built in. – Jampacked

Answer 2

In case, that firebug is closed, I overwrite the console object. So, you can implement fallback functions ...

console = console || { log : function() {
// place your logging code here, if firebug is closed
}, debug : function() {
// place your debug code here, if firebug is closed
} /*, [ and so on .. ] */ };

Greetings,

Dyvor

Major

Answer 3

In FireFox if the console isn't open when you call to it a JavaScript error is thrown.

I wrap all my console.log's in a wrapper to check for console - you can either wrap the check around the console call or use a different name to alias console.

Aliasing

/* konsole is a safe wrapper for the Firebug console. */
var konsole = {
  log: function(args){},
  dir: function(args){},
  debug: function(args){},
  info: function(args){},
  warn: function(args){},
  error: function(args){}
};
// Remove below here when in production
if (typeof window.console != 'undefined' && typeof window.console.log == 'function') {
  konsole = window.console;
}
konsole.log('testing debugging');
konsole.error('throw an error message to the console');

Check for console

if (typeof window.console != 'undefined' && typeof window.console.log == 'function') {
  console.log('testing debugging');
  console.error('throw an error message to the console');
}

Chuipek

Answer 4

I always do a if (console) check to make sure the console actually exists. If firebug isn't open it's like you're acting upon a null object, thus why it breaks.

Papilloma

A null object would silently swallow the logging, which would work fine... – Heteromerous

@delnan: I think what bobber means is that console has the value null (which is not true, it is undefined). But in both cases the code will break. – Fernando

@Felix: I know what he propably meant, I was just being pedantic. – Heteromerous

@delnan. Shallow and pedantic. ;) – Papilloma

Answer 5

Firefox doesn't have a console object. Firebug adds one.

The simply fix is to have firebug open for development and remove console.log statements for deployment.

you can also make a custom log function like

function log (msg)
{
  if(console)
  {
    console.log(msg);
  }
}

that will log only if console exists

Andromeda

the problem with this function is that it won't accept multiple arguments and parameters the same way console.log() does and also if(console) is not really a good check for if an object is defined or not in javascript. – Hypermetropia

the code snipit wasn't intended to be functional, just to get the idea across. I'd post a real example but you beat me too it :p – Andromeda

Answer 6

To keep Firefox 3.0 from complaining reliably use the following...

if ('console' in window) {}

Pundit