Can I view the result of a callback function using console.log() in Firebug?

Question

Using the example below, is it possible to send the result of the callback function to the console, i.e. the value being returned?

rows.sort(function(a, b) {
 if(a.sortKey < b.sortKey) return -sortDirection;
 if(a.sortKey > b.sortKey) return sortDirection;
 return 0;
 });

What would I use as the argument: console.log(?)

Answer 1

You could always log before you return, and refactor to support easy logging. Other than that, the return value is lost to the sort function.

rows.sort(function(a, b) {
 var returnVal = 0;
 if(a.sortKey < b.sortKey) returnVal = -sortDirection;
 else if(a.sortKey > b.sortKey) returnVal = sortDirection;

 console.log( returnVal );
 return returnVal;
 });

Answer 2

You can always take advantage of functions being first class objects in Javascript, and play around with AOP-like wrapping:

function addLogging(fn){
  return function() {
    var result = fn.apply(null, arguments);
    console.log(result);
    return result;
  }
}

var sortDirection = 1;

[ {sortKey: 1}, {sortKey: 2}, {sortKey: 0} ].sort(addLogging(function(a, b){
  if(a.sortKey < b.sortKey) return -sortDirection;
  if(a.sortKey > b.sortKey) return sortDirection;
  return 0;
}));