console.log有时不起作用

Question

I have encountered this several times, & there is no explanation for it. There was no JS errors on the site. The code is indeed being executed. Replacing them with alert() works just fine.

So today that happened again, so I tried to check the console object in the console object & I found some irregularities as if something has overwritten the console object.

The following screenshot is of the site (site A) where I have this problem:

http://ompldr.org/vZ256Mw/Selection_004.jpg

You see how log, warn & info are empty functions? and the console object is different from how it is on a site (site B) where console works fine (screenshot follows)?

http://ompldr.org/vZ256Mg/Selection_003.jpg

Now the code running on both the sites is exactly same. Site B is my local install and Site A is staging and I don't have anything in the code which overwrites the console object, so what could be an explanation for this behavior?

---

As per nfroidure's suggestion, I added that code in my head section before anything else and I got this: uncaught error! (anonymous function) (anonymous function) uncaught error! (anonymous function) (anonymous function) , second of which points to a code in another library file which has the following in it:

if (!("console" in window) || !("firebug" in console))
{
    var names = ["log", "debug", "info", "warn", "error", "assert", "dir", "dirxml",
    "group", "groupEnd", "time", "timeEnd", "count", "trace", "profile", "profileEnd"];

    window.console = {};
    for (var i = 0; i < names.length; ++i)
        window.console[names[i]] = function() {}
}

This is responsible because I think the if check is faulty. "console" in window will be true & "firebug" in window will be false for me in Chrome resulting in replacing the console methods. It should be && over there, no?

Update: After changing the operator to && it started to work on Site A, but I don't understand why it only gets triggered on one and not on another.

Answer 1

看起来Site A有firebug，因为console的方法看起来很像这里的方法： http ： //getfirebug.com/wiki/index.php/Console_API

Answer 2

Try to add this on the top of your document :

<script>
(function(){
    var wc=window.console;
    delete window.console;
    window.__defineGetter__("console", function(){
        return wc;
        });

    window.__defineSetter__("console", function(val){
        throw('error!');  // Look at js stack when throwed
        });
})();
</script>