wheresrhys

I’m always dismayed by the lack of debugging information out there. Yes, there is plenty of information on how to fix particular bugs, but very little on the more general heuristic processes for finding the source of a bug. This may be because debugging is, by its very nature, a thankless process of trial and error.

But nevertheless, I’ve just discovered for myself (though it may be common practice for others already) a technique for debugging when the bug lies within a function which runs numerous times without fail, but when fired on another particular occasion, fails. For example, you have one function which creates shopping basket items from all your user’s saved data at startup, but when you try and use the same function later to create another item based on user input, the function fails.

Putting some var_dump() [php] or console.log() [javascript] calls inside the function will result in reams of information being printed out, most of it useless as its produced by the successfully running first calls to the function. So what I now do is this:

Change

function myFunction(param1, param2, ..., paramN) {
    some = code;
    console.log(something);
    some = more(code);
}

to

myFunction(param1, param2, ..., paramN, test) {
    var some = code;
    if(test) {
        console.log(something);
    }
     some = more(code);
}

And change the function call that needs debugging from

myFunction(a, b, ... N)

to

myFunction(a, b, ... N, true)

Now you will only be shown the debugging messages when you need them. It’s particularly useful for javascript as the console area of firebug is so small so its good to limit messages to only those which are relevant.