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How can I delete the same object in two arrays using lodash or underscore?

Now I have two arrays of objects,

var arr1 = [{id: 0, name: 'Jack'}, {id: 1, name: 'Ben'}, {id: 2, name: 'Leon'}, {id: 3, name: 'Gavin'}];
var arr2 =  [{id: 0, name: 'Jack'}, {id: 5, name: 'Jet'}, {id: 2, name: 'Leon'}];

I want to delete those objects the same id

in arr1

and arr2

so the results are:

var arr1 = [{id: 1, name: 'Ben'}, {id: 3, name: 'Gavin'}];
var arr2 =  [{id: 5, name: 'Jet'}];

How do I implement it with lodash

or underscore

?

Here is my implementation.

arr1_ids = _.pluck(arr1, 'id');
arr2_ids = _.pluck(arr2, 'id');

same_ids = _.intersection(arr1_ids, arr2_ids);

arr1 = _.remove(arr1, function(e) { return !_.contains(same_ids, e.id); });
arr2 = _.remove(arr2, function(e) { return !_.contains(same_ids, e.id); });

Is there a better way to do this?

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3 answers


Can you use _.difference?



same_elements = _.intersection(arr1, arr2);
arr1 = _.difference(arr1, same_elements);
arr2 = _.difference(arr2, same_elements);
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I'm not sure how to do this with underscore or lodash, but here's a JavaScript implementation.

It creates a filter function that can then be applied to both arrays to keep only the elements that are not part of the intersection.



var arr1 = [{id: 0, name: 'Jack'}, {id: 1, name: 'Ben'}, {id: 2, name: 'Leon'}, {id: 3, name: 'Gavin'}];
var arr2 =  [{id: 0, name: 'Jack'}, {id: 5, name: 'Jet'}, {id: 2, name: 'Leon'}];

var negative_intersection_filter = function(a, b) {
  // create a map to speed up the filtering later
  var map = a.reduce(function(map, current) {
    // perform the intersection
    map[current.id] = b.some(function(item) {
      return item.id == current.id;
    });
    return map;
  }, {});

  // our filtering function, simple
  return function(item) {
    return !map[item.id];
  }
}(arr1, arr2);

// apply the filter here
arr1 = arr1.filter(negative_intersection_filter);
arr2 = arr2.filter(negative_intersection_filter);
console.log(arr1);
console.log(arr2);
Run codeHide result


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I think your algorithm is right, here's a slightly different approach in simple js. I used a, b

instead arr1, arr2

for brevity:

// Collect ids and sort
var ids = a.map(function(obj) {return obj.id}).concat(b.map(function(obj) {return obj.id})).sort();

// Get IDs that aren't duplicates
var nonDups = ids.filter(function(v, i, o){return v !== o[i-1] && v !== o[i+1]});

// Keep only the non-duplicates in each array
a.reduceRight(function(pre, cur, i, o){if (nonDups.indexOf(cur.id) == -1) o.splice(i, 1)},0);
b.reduceRight(function(pre, cur, i, o){if (nonDups.indexOf(cur.id) == -1) o.splice(i, 1)},0);

JSON.stringify(a)  // [{"id":1,"name":"Ben"},{"id":3,"name":"Gavin"}]
JSON.stringify(b)  // [{"id":5,"name":"Jet"}]

reduceRight is just used to iterate backward through each array, so splicing doesn't affect the iteration.

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