SOURCE

function copy(arr) {
  var obj = arr.construcrot === Array?[]:{};
  for(var item in arr) {
		if(typeof arr[item] === 'Object') {
      obj[item] = copy(arr[item]);
    }else {
			obj[item] = arr[item];
    }
  }
  return obj;
}

var arr = {
  "a":1,
  "b":2,
  "c":3
}
console.log(arr.a);
var brr = copy(arr);
brr.a = 2;
console.log(brr.a);