How to safely wrap `console.log`?

Question

Suppose I want to include some calls to console.log for some legitimate production reason, say for something like a unit test harness. Obviously I would not want th

Answer 1

Paul Irish has a nice light wrapper/replacement for console.log().

http://paulirish.com/2009/log-a-lightweight-wrapper-for-consolelog/

Advantages:

• Prevent errors if a console isn’t around (i.e. IE)
• Maintains a history of logs, so you can look in the past if your console is added afterwards (e.g. firebug lite)
• Light & simple.
• Very quick to type -- log() or window.log().

Answer 2

Try using the code snippet below... (this is my preferred approach because it makes you independent of window.console)

var logger = (function (c) {
    "use strict";
    var m = {
        log: function (a, t) {
            if (!c) { return; /* return or call your custom function here */ }
            var l = c.log,
                f = t === undefined ? l : (this.__dict__[t] || l);
            f.apply(c, a)
        },
        __dict__: {
            "trace": c.trace,
            "debug": c.debug,
            "info": c.info,
            "warn": c.warn,
            "error": c.error
        }
    };

    return {
        trace: function () { m.log(arguments, "trace"); },
        debug: function () { m.log(arguments, "debug"); },
        info: function () { m.log(arguments, "info"); },
        warn: function () { m.log(arguments, "warn"); },
        error: function () { m.log(arguments, "error"); },
        log: function () { m.log(arguments, undefined); }
    };
}(window.console))

So you may now try these in your code and see the result

logger.info("Hello");
logger.trace("Hello");
logger.debug("Hello");
logger.warn("Hello");
logger.error("Hello");
logger.log("Hello");

Answer 3

As a slight variation on Chris' answer, simply define 'log' as a property of 'console' with an empty function:

if (typeof console === "undefined") {
    console = {
        log: function () {
            return;
        } 
   };
}

Answer 4

Sorry, there was a bug in my post. Don't know how I missed it.

The PROPER way to create a global console object, if it does not exist:

if (typeof console === "undefined"){
    console={};
    console.log = function(){
        return;
    }
}