Question

Filtering works fine for an object (data) wrapping around an array of objects:

var arr = {"data":
 [
  {"name":"Alan","height":"171","weight":"66"},
  {"name":"Ben","height":"182","weight":"90"},
  {"name":"Chris","height":"163","weight":"71"}
 ]
};

var new_arr = $.extend(true, arr);

new_arr.data = $.grep(new_arr.data, function(n, i){
  return n.weight > 70;
});

alert(new_arr.data.length); // answer is 2

However, filtering without the object wrapper doesn’t.

var arr = [
  {"name":"Alan","height":"171","weight":"66"},
  {"name":"Ben","height":"182","weight":"90"},
  {"name":"Chris","height":"163","weight":"71"}
 ];

var new_arr = $.extend(true, arr);

new_arr = $.grep(new_arr, function(n, i){
  return n.weight > 70;
});

alert(new_arr.length); // answer is 1 instead of 2

I am not sure where is the problem. Can anyone point out. Thanks!

Answer 1

You’re using extend incorrectly. You can’t extend the new_arr with an array. Extend will add methods/props to an object but what methods/props will it create when it runs into your array? This is why it works with the object wrapper: 1) extend expects an object and 2) ‘data’ is a property that can be added to new_arry.

Despite, in your second example, it doesn’t look like you need to extend anything. Does this work?

new_arr = $.grep(arr, function(n, i){ // just use arr
  return n.weight > 70;
});