Intersection and Equals between arrays of objects by only some fields with underscore.js

Question

I'm using underscore.js on my project and i want to compare two arrays but only their intersection by one field.

The first array :

[{item: myObject1, label: myObject1.name, ticked: true, disabled: false}]

the second array :

[{item: myObject1, label: myObject1.name, ticked: false, disabled: false}, 
{item: myObject2, label: myObject2.name, ticked: true, disabled: false}]

I want to return intersection of these arrays by myObject.id and compare it :

intersection :

{item: myObject1, label: myObject1.name, ticked: true, disabled: false}

and

{item: myObject1, label: myObject1.name, ticked: false, disabled: false}

because myObject1 is the intersection (myObject1.id == myObject1.id).

these items are not equals because the first element is ticked and the second no... so, return false;

I don't see how can i do that with underscore.js.

EDIT:

with only isEqual function, i can do that (i use AngularJS):

isIOEquals: function(inputs, outputs){
        var editedInputs = [];
        var editedOutputs = [];
        angular.forEach(outputs, function(outputItem){
            angular.forEach(inputs, function(inputItem){
                if(_.isEqual(inputItem.item.id, outputItem.item.id)){
                    editedInputs.push(inputItem);
                    editedOutputs.push(outputItem);
                }
            });
        });

        return _.isEqual(editedInputs, editedOutputs);
    }

possible duplicate of [How to use underscore's "intersection" on objects?](http://stackoverflow.com/questions/8672383/how-to-use-underscores-intersection-on-objects) — Vladu Ionut, Mar 01 '15 at 14:56
Just to be clear, you want the intersection, but you want it to ignore everything but the item attribute? — demux, Mar 01 '15 at 15:02
Yes. For the intersection, i want to ignore everything except the object id (myObject.id). After that, i want to compare the elements of the intersection. — slim, Mar 01 '15 at 15:06
wich objets ? there are two arrays at the begining ("the first" and "the second" in the question). — slim, Mar 01 '15 at 15:12
and the result of intersection is two objects because i have to compare it. — slim, Mar 01 '15 at 15:13
Do you mean `.item.id`? There are no `myObject`s in your arrays. — Bergi, Mar 01 '15 at 15:15

score 1 · Accepted Answer · answered Mar 01 '15 at 15:59

I believe this will do the job.

function myIntersection() {
    var objectLists = [].slice.call(arguments),
        objMapper = objectLists.pop();

    var flatLists = objectLists.map(function(lst) {
        return lst.map(objMapper);
    });

    // There will be duplicates in this list, but maybe that's the desired
    // behaviour, so I'll leave it to you to sort that out.
    var mergedObjectLists = _.flatten(objectLists);

    var intersectingValues = _.intersection.apply(null, flatLists);
    return mergedObjectLists.filter(function(obj) {
        return intersectingValues.indexOf(objMapper(obj)) !== -1
    });
}

myIntersection(list1, list2, function(obj) {return obj.item.id});

I'd love to see other approaches.

Ok. sorry but it's more complicated than my approach. finally, i used my solution... — slim, Mar 11 '15 at 13:15

Intersection and Equals between arrays of objects by only some fields with underscore.js

1 Answers1