How can I make Javascript parameters default to something if not present?

I have this function:

this.checkButton = function (buttonName, element, expectedPresent, expectedEnabled) {
    var enabledCheck = expectedEnabled ? "enabled" : "disabled";
    it('Find a ' + buttonName + ' button and check it is ' + enabledCheck, function () {
        expect(element.isPresent()).toBe(expectedPresent);
        expect(element.isEnabled()).toBe(expectedEnabled);

    });
}

Is there a way I can make this so that if the function is called without the last two parameters then those parameters will both default to true?

Answer

If I understood what you want.

Try to say in starting of function.

expectedPresent = (expectedPresent==undefined) ? true : expectedPresent;
expectedEnabled = (expectedEnabled==undefined) ? true : expectedEnabled;

I hope this helps.