Recursively remove null values from JavaScript object

Question

I have a JSON obj, after some operations (like delete some pieces), I print it and everything looks good except that I have some null values. How do I remove th

Answer 1

The following is a modification to the answer by @Phrogz. If book[3] was also null, the answer given would not remove the last null because the array's length would be less than k in last loop's iteration.

The following would work by performing a second call to the array:

function removeNulls(obj) {
  var isArray = obj instanceof Array;
  for (var k in obj) {
    if (obj[k] === null) isArray ? obj.splice(k, 1) : delete obj[k];
    else if (typeof obj[k] == "object") removeNulls(obj[k]);
    if (isArray && obj.length == k) removeNulls(obj);
  }
  return obj;
}