比较两个对象的JavaScript数组并删除常见的数组对象

Question

var a = [
  [
    {
      id: "AAA"
    },
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "DDD"
    }
  ]
];
var b = [
  [
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "CCC"
    },
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "AAA"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "CCC"
    },
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "AAA"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "BBB"
    }
  ]
];

function remove_duplicates(a, b) {
    for (var i = 0, len = a.length; i < len; i++) {
        for (var j = 0, len = b.length; j < len; j++) {
            if (a[i].name == b[j].name) {
                b.splice(j, 1);
            }
        }
    }

    console.log(a);
    console.log(b);

}

console.log(a);
console.log(b);

remove_duplicates(a,b);

I have tried the filter and reduce but they are coming with desired result I found a similar one but the one I have got little different structure

seeking for possible solution from JavaScript or underscore

expected result: [[{"id":"BBB"}],[{"id":"CCC"},{"id":"BBB"}],[{"id":"AAA"}],[‌​{"id":"DDD"}],[{"id"‌​:"CCC"},{"id":"DDD"}‌​]]

Answer 1

First we need to know when two arrays are equal. I have defined this in the isEqual function such that an array is equal to another array if they are the same length and the objects have the same id in the same order.

Next, we need to understand what it means to 'remove duplicates'. Imagine if you have two arrays of numbers. [1,2,3,4] and [2,4,5,6]. We'll expect the result to be [1,3,5,6]. We do this by getting the first array and subtracting any items that exist in the second array and then getting the second array and subtracting any items that exist in the first array. Finally we join the two results together. This is what is happening in the remove_duplicates function.

var a = [
  [
    {
      id: "AAA"
    },
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "DDD"
    }
  ]
];
var b = [
  [
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "CCC"
    },
    {
      id: "BBB"
    }
  ],
  [
    {
      id: "AAA"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "CCC"
    },
    {
      id: "DDD"
    }
  ],
  [
    {
      id: "AAA"
    }
  ],
  [
    {
      id: "AAA"
    },
    {
      id: "BBB"
    }
  ]
];

function remove_duplicates(a, b) {
  var setOfB = setOf(b);
  var setOfA = setOf(a);

  var aMinusB = minus(setOfA, setOfB);
  var bMinusA = minus(setOfB, setOfA);
  return aMinusB.concat(bMinusA);
}

function setOf(array){
  return _.uniq(array, false, JSON.stringify);
}

function minus(a,b) {
  return _.reject(b, function(item){
    return _.find(a, _.partial(_.isEqual, item));
  });
}


// var expected = [
//   [{"id":"BBB"}],
//   [{"id":"CCC"},{"id":"BBB"}],
//   [{"id":"AAA"}],
//   [{"id":"DDD"}],
//   [{"id":"CCC"},{"id":"DDD"}]
// ];


console.log(remove_duplicates(a,b));