Call/Apply

example.js

// You wrote this line
Function.prototype.call(current[ev], this, arguments);


// This line does what I want, calling the method on the current tool and passing the arguments.
current[ev].apply(this, arguments);

// Not sure what you were aiming for with the other line?

Caveat that I ran into today: using call/apply on Function.prototype invokes it as expected, but returns undefined.