Question

I see this throughout our codebase:

(function(undefined) {
    var foo = {
        dirtyRow: undefined,
        dirtyCells: undefined,
        ...
        clearDirty: function () {
            this.dirtyRow = undefined;
            this.dirtyCells = undefined;
        }
    }
})();

Can someone articulate for me what’s wrong with this? What should we be doing instead?

Answer 1

null makes more sense than undefined in this context, because you are defining the variables but are not yet assigning a value to them.

However both null and undefined are falsy values, so for the most part the behaviour will be the same.

null is a keyword though, whereas undefined is not. So null would be more “reliable”, even if you are using the argument to ensure that undefined is in fact undefined.