Remove elements from array with another array containing duplicates javascript

Question

I have 2 arrays, I want to delete the elements from first array with the second ones just once conserving the other duplicates that might be:

array1 = [1,1,1,1,2,2,2,2];
array2 = [1,1,2];

//resultingArray = [1,1,2,2,2];

It seems that all the answers I got are about removing duplicates while searching for this..

I'm wondering if there's a way to do this with filter, but it only seems to filter all the entries

resultingArray = array1.filter(function(el){
   return array2.indexOf(el) === -1;
});

//resultingArray = [];

Another way that I could think of is removing each one of the array elements one by one like this

for( var i = 0; i < arr.length; i++){ 
   if ( arr[i] === Number) {
     arr.splice(i, 1);
     i = arr.length;
};

But it doesn't seem to be a great way to do this?

And again the difference between those arrays will remove all the duplicated elements

Would appreciate to know the best method for this or directions to a duplicated posts that i couldn't find!!

should be array2.indexOf(el) not array2.indexOf(i, el) though it's very heard to understand that first sentence. — Pointy
– Pointy, Commented Feb 16, 2020 at 12:18

Rory McCrossan · Accepted Answer · 2020-02-16 12:18:44Z

1

To achieve this you can loop through array2 removing the first matching item matching the current value in array1. Something like this:

let array1 = [1,1,1,1,2,2,2,2];
let array2 = [1,1,2];

array2.forEach(i => array1.splice(array1.indexOf(i), 1));

console.log(array1);

answered Feb 16, 2020 at 12:18

Rory McCrossan

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2 Comments

Yeas!! I see, referencing the index to the splice was so simple that I couldn't see it!! Thank you Rory!

Note that the answer removes the last element from array1 for each element of array2 that can't be found in array1.