How to debug JavaScript closure state?

Question

I have this code snippet that scientifically accurate calculates the speed of a cat according to the amount of legs it has.

function Cat()
{
    var self = this;

    var _legs = 0;

    self.addLeg = function()
    {
        _legs++;
    }

    self.speed = function()
    {
        return Math.pow(_legs,1.5)*2;
    }
}

Chrome Debugger

When I try to debug one of my cats, how can I see the inner variables, like _legs :

• without adding extra code just to expose it,
• nor 'actively' executing functions in the cat (that might change state)?

Answer 1

You can't expose a variable without exposing it. You should, however, be able to see the state of _legs while stepping through the constructor, addLeg and speed functions.