Question

Where do the arguments a and b come from in this sorting function?
Are they passed automatically?

dir = "asc"
sortArray = new Array("hello", "Link to Google", "zFile", "aFile");

//sort array
if (dir == "asc") {
    sortArray.sort(function(a, b) {
        return a.toLowerCase() > b.toLowerCase()
    });
} else {
    sortArray.sort(function(a, b) {
        return b.toLowerCase() > a.toLowerCase()
    });
}

    for (var i = 0; i < sortArray.length; i++) {
    console.log(sortArray[i]);
}

Answer 1

Are they passed automatically?

Yes.

You are creating an anonymous comparator function, which the sort function calls whenever it needs to compare two objects.