Can 'this' ever be null in Javascript

I have a function along the lines of the following:

    doSomething: function () {
        var parent = null;

        if (this === null) {
            parent = 'some default value';
        } else {
            parent = this.SomeValue();
        }
    }

Could parent ever be set to 'some default value' or is the check for null superfluous?

Alternatively, what if I used the less restrictive:

    doSomething: function () {
        var parent = this ? this.SomeValue() : 'some default value';
    }

Could parent ever be set to 'some default value' in this case?