javascript array error: array[n] is undefined

relevant code:

function stepNetwork() {
    for(i = 0; i<maxNeurons; i++) {
        if(neuronArray[i].charge >= neuronArray[i].threshhold) {
            var elapsed = ((new Date()).getTime()) - neuronArray[i].lastFired;
            if(elapsed >= 5000){
                fireNeuron(i);
            }
        }
    }
}

function fireNeuron(n){
    //get number of outputs on this neuron
    var outs = neuronArray[n].outputs.length;
    for(p = 0; p < outs; p++) {
        sendChargeTo = neuronArray[n].outputs[p];
        addCharge(sendChargeTo);
    }
    neuronArray.charge = 0;
    neuronArray.lastFired = ((new Date()).getTime());
}

function addCharge(n) {
    neuronArray[n].charge++;//HERES THE ERROR!!
}

Here is what firebug is telling me:

neuronArray[n] is undefined ///then why can I see its value in the scripts->watch tab?
addCharge(n=100)js_operation.php (line 73)
fireNeuron(n=73)js_operation.php (line 66)
stepNetwork()

The 开发者_StackOverflow社区thing that gets me is that when I pass a number it works, and when I evaluate neuronArray, neuronArray[n], neuronArray[n]. charge etc in the scripts pane (watch area), it always is able to reference it.

Maybe this is the problem:

sendChargeTo = neuronArray[n].outputs[p];
addCharge(sendChargeTo);

You're not sending addCharge an index, you're sending it neuronArray[n].outputs[p].

Apart from Raynos's comments about the last two lines in fireNeuron I can't see an obvious problem.

Perhaps you have a globals problem? I think that variables i, p, and sendChargeTo should be declared local with var.