How to remove elements from an array using values stored in another array

Question

I have two arrays

var a = ['tayyar', '14march' ];

and

b = [{

    "feedsource": "tayyar",  
    "hash": "46cc3d067df1ea7877140c67b60e9a7a"
}, {

    "feedsource": "elmarada",
    "hash": "a9fb75f2aa4771945ec597ecf9ae49ea"
}, {

    "feedsource": "14march",
    "hash": "fce7a6a87b53358c4be47507b0dc327b"
}, {

    "feedsource": "tayyar",    
    "hash": "b85d2a9c22ac4831477de15ba24b4ac5"
}]

I want to remove objects from b whose feedsources are not defined in a.

So far I have tried

 b.forEach(function(e) {    

                            var indexVal = b.indexOf(e);

                            if(a.indexOf(e.feedsource) ==-1){

                                 console.log(e.feedsource);

                                 b.splice(indexVal,1);

                             }                                                                          
                        });

But it doesnt seems to work and I still see the elements that shouldn't be there as well as elements that should be there getting removed. What am I doing wrong in my function ?

Madara's Ghost · Accepted Answer · 2015-07-29 11:35:12Z

2

A better solution would be to not alter the original array, but instead creating a new, filtered array. Luckily, JavaScript provides .filter() to help you with that!

var c = b.filter(function(el) {
    // Only keep those where the following is true
    return a.indexOf(el.feedsource) > 0;
});

answered Jul 29, 2015 at 11:35

Madara's Ghost

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5 Comments

Bazinga777 Over a year ago

Thanks, I don't mind this if it works. let me give it a shot and see if this works.

Paddy Over a year ago

Worth noting that if you are supporting old IE, you will need a polyfill for this. Can find one here: developer.mozilla.org/en/docs/Web/JavaScript/Reference/…

Madara's Ghost Over a year ago

@Paddy We're in 2015. If he needs to support old IE, he knows his workflow is bound to be abnormal. And in all case, may God have mercy upon his soul.

Paddy Over a year ago

@MadaraUchiha - there are quite a few of us around constrained by clients :) It's still something worth noting.

Bazinga777 Over a year ago

I am not supporting old IE so this shouldnt be a problem and it worked well

Adam Boduch · Accepted Answer · 2015-07-29 17:46:12Z

0

Create a filtered array with lodash filter():

_.filter(b, function(item) {
    return _.includes(a, item.feedsource);
});

Mutate the existing array with lodash remove():

_.remove(b, function(item) {
    return _.includes(a, item.feedsource) === false;
});

answered Jul 29, 2015 at 17:46

Adam Boduch

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