phiggins42 · April 16, 2012 12:01
diff --git a/sorter.html b/sorter.html
 <!DOCTYPE html>
 <html>
 <head>
    <script>
    
    var list = [0, -1, 1, -1, 0, null, 1];
    
    var sorter = function(direction){
        // returns a sort function which treats `null` as a special case, either 'always higher' (1)
        // or 'always lower' (-1)
        
        direction = direction || 1;
        var up = direction > 0;
        
        return function(a, b){
            var aa = a == null ? undefined : a,
                bb = b == null ? undefined : b,
                careabout = up ? aa : bb
            ;
            return aa == bb ? 0 : aa > bb || careabout == undefined ? 1 : -1;
        }
        
    }

    var higher = [].concat(list.sort(sorter(1)));    
    var lower = [].concat(list.sort(sorter(-1)));

    console.log(lower[0] === null, lower);
    console.log(higher[higher.length - 1] === null, higher);

    // then, something that sorts something in a direction can use that direction to
    // determine where the nulls end up. `list` above ranged from negative-one to one, 
    // with mixed zero and null values in between. If we want to view that list 
    // from highest value to descending, we'd want the nulls to be treated as 
    // 'always lower' so they appear at the end of the list.
    // If we wanted to view the list from lowest value to highest value we'd want the
    // nulls to be treated as `higher-than-anything` so they would appear at the bottom
    // list.
    
    var sortThisArray = function(arr, direction){
        var s = sorter(direction);
        return arr.sort(function(a,b){
           return direction * s(a,b) 
        });
    }
    
    console.log(sortThisArray(list, 1));
    console.log(sortThisArray(list, -1));

    </script>
    
 </head>
 <body>
 </body>
 </html>
	<!DOCTYPE html>
	<html>
	<head>
	<script>

	var list = [0, -1, 1, -1, 0, null, 1];

	var sorter = function(direction){
	// returns a sort function which treats `null` as a special case, either 'always higher' (1)
	// or 'always lower' (-1)

	direction = direction \|\| 1;
	var up = direction > 0;

	return function(a, b){
	var aa = a == null ? undefined : a,
	bb = b == null ? undefined : b,
	careabout = up ? aa : bb
	;
	return aa == bb ? 0 : aa > bb \|\| careabout == undefined ? 1 : -1;
	}

	}

	var higher = [].concat(list.sort(sorter(1)));
	var lower = [].concat(list.sort(sorter(-1)));

	console.log(lower[0] === null, lower);
	console.log(higher[higher.length - 1] === null, higher);

	// then, something that sorts something in a direction can use that direction to
	// determine where the nulls end up. `list` above ranged from negative-one to one,
	// with mixed zero and null values in between. If we want to view that list
	// from highest value to descending, we'd want the nulls to be treated as
	// 'always lower' so they appear at the end of the list.
	// If we wanted to view the list from lowest value to highest value we'd want the
	// nulls to be treated as `higher-than-anything` so they would appear at the bottom
	// list.

	var sortThisArray = function(arr, direction){
	var s = sorter(direction);
	return arr.sort(function(a,b){
	return direction * s(a,b)
	});
	}

	console.log(sortThisArray(list, 1));
	console.log(sortThisArray(list, -1));

	</script>

	</head>
	<body>
	</body>
	</html>