Remove object from array if it is contained in another array

Question

I am trying to remove an object from an array, if that object's property (unique) is included in the other array. I know I can do a nested for-loop like this:

for(i = 0; i < array.length; i++) {
    for(j = 0; j < array2.length; j++) {
        if(array[i].Email === array2[j].Email) {
            //remove array[i] object from the array
        }
    }
}

Or whatever. Something like that. Is there an ES6 filter for that? I can easily do a filter up against a regular array with strings, but doing it with an array of objects is a bit more tricky.

@Rajesh Object has an "Email" property. That should be fine. — MortenMoulder
– MortenMoulder, Commented Oct 17, 2016 at 9:23
Are you trying to delete the key, remove the value/ reference or remove the value from memory? — maximumcallstack
– maximumcallstack, Commented Oct 17, 2016 at 9:24
@evolutionxbox ECMAScript is probably what I should call it. I still haven't figured the difference out. — MortenMoulder
– MortenMoulder, Commented Oct 17, 2016 at 9:25

double-beep · Accepted Answer · 2024-06-11 07:30:08Z

11

If you are fine using ES6, you can even look into array.find, array.filter or array.some.

`Array.findIndex`

const result = array.filter(x => {
    return array2.findIndex(t => t.Email === x.Email) === -1;
});

`Array.some`

const result = array.filter(x => {
    return !array2.some(t => t.Email === x.Email);
});

edited Jun 11, 2024 at 7:30

double-beep

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answered Oct 17, 2016 at 9:31

Rajesh Dixit

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Comments

gurvinder372 · Accepted Answer · 2016-10-17 09:46:10Z

3

Not very optimal, but try this

array = array.filter( function( item ){
  return array2.filter( function( item2 ){
    return item.Email == item2.Email;
  }).length == 0;
});

Try with find as well, it won't iterate all the elements and will break after first match itself

array = array.filter( function( item ){
  return array2.find( function( item2 ){
    return item.Email == item2.Email;
  }) == undefined;
});

edited Oct 17, 2016 at 9:46

answered Oct 17, 2016 at 9:25

gurvinder372

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9 Comments

MortenMoulder Over a year ago

Yeah that works. Thanks! Is that the best way, though? I'm assuming the fastest would be O(n^2) anyway?

gurvinder372 Over a year ago

@Snorlax fastest way would be to index unique email-ids from both arrays and then match each item one by one. In that case, complexity would O(2n)

MortenMoulder Over a year ago

Yeah. With < 10 items, this should be fast enough though.

gurvinder372 Over a year ago

@Snorlax with less than 10 items, there shouldn't be any problem.

Rajesh Dixit Over a year ago

I would suggest you use array.findIndex or array.find or array.some. We do not need to find all elements and should break upon first match

|

Nina Scholz · Accepted Answer · 2016-10-17 09:31:25Z

3

You could use a Set with ES6

var array = [/* your data */],
    array2 = [/* your data */],
    set = new Set(...array2.map(a => a.Email));

array = array.filter(a => !set.has(a.Email));

answered Oct 17, 2016 at 9:31

Nina Scholz

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3 Comments

MortenMoulder Over a year ago

Doesn't look like my Typescript validation is happy about Set.. hmm.

Nina Scholz Over a year ago

es6 !== typescript.

MortenMoulder Over a year ago

I never said that it was.

Pumayk26 · Accepted Answer · 2016-10-17 09:29:26Z

-1

Try this one.... :)

if(array[i].Email === array2[j].Email){
   // splice(Index you want to remove,to witch element)
   array1.splice(i,1);
}

splice() can remove element of your array. You need to pass witch element. witch element is the start of delete. How many elements should delete. That's 1.. :)

answered Oct 17, 2016 at 9:29

Pumayk26

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1 Comment

MortenMoulder Over a year ago

n.. no. That's not what I want.

Emil S. Jørgensen · Accepted Answer · 2016-10-17 09:32:42Z

-1

How about writing a function, passing the parameters and simply collecting the output?

function arrNotInArrKey(arr1, arr2, key) {
  for (var i = 0; i < arr1.length; i++) {
    for (var j = 0; j < arr2.length; j++) {
      if (arr1[i][key] === arr2[j][key]) {
        arr1.splice(i, 1);
        i--;
      }
    }
  }
  return arr1;
}
console.log(
  arrNotInArrKey([{
    name: 1
  }, {
    name: 3
  }, {
    name: 2
  }], [{
    name: 2
  }], "name")
);

answered Oct 17, 2016 at 9:32

Emil S. Jørgensen

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Comments

Harun KARATAŞ · Accepted Answer · 2016-10-17 09:35:19Z

-2

You can use shift function. here it's example.

http://www.w3schools.com/js/tryit.asp?filename=tryjs_array_shift
for(i = 0; i < array.length; i++) {
    for(j = 0; j < array2.length; j++) {
        if(array[i].Email === array2[j].Email) {
            array.shift(array[i].Email);
        }
    }
}

answered Oct 17, 2016 at 9:35

Harun KARATAŞ

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