Object Method As Event Listener

I want each instance of an object to be able to listen for input events.
When the event occurs, a method of the object should be called, such
that "this" is in scope and refers to the object instance.

Is this possible? Example:

function MyConstructor(element)
{
//element is some HTML element
this.addListeners(element);

this.foo = "Bar";

return this;
}

MyConstructor.prototype.addListeners = function(element)
{
element.addEventListener("keypress", this.doSomething, true);
}

MyConstructor.prototype.doSomething = function(e)
{

alert(this.foo.length); //Error: this.foo has no properties

alert(this);
//shows the HTML element that triggered the event
}

Is there any way to get "this" to refer to the object in the event listener?