Filtering an array against another array

Question

I have 2 arrays like this ...

var heroes = [{
    name: "Batman",
    franchise: "DC"
  },
  {
    name: "Ironman",
    franchise: "Marvel"
  },
  {
    name: "Thor",
    franchise: "Marvel"
  },
  {
    name: "Superman",
    franchise: "DC"
  }
];

var stars = ["Thor", "Superman"];

var marvelHeroes = heroes.filter(function(hero) {
  return stars.indexOf(hero.name) >= 0;
});

console.log(marvelHeroes);

This code is returning 'undefined'. So essentially I am trying to filter an array against values in another array.

Can someone please advise what am I doing wrong ? Thanks

My expected output is an array of objects like the following ...

[
{name: "Thor", franchise: "Marvel"},
{name: "Superman", franchise: "DC"}
];

I have seen a similar question here, but that solution is not working for me ...

Which hero are you trying to select? Select with hero[index].name — AA Shakil
– AA Shakil, Commented Jun 10, 2018 at 13:46
I converted your code to a snippet and logged the object to the console. It works as expected. — 31piy
– 31piy, Commented Jun 10, 2018 at 13:55

Sajeetharan · Accepted Answer · 2018-06-10 13:59:39Z

1

It should be just return stars.indexOf(item.name) !== -1 ;

DEMO

var heroes = [
    {name: "Batman", franchise: "DC"},
    {name: "Ironman", franchise: "Marvel"},
    {name: "Thor", franchise: "Marvel"},
    {name: "Superman", franchise: "DC"}
];

var stars = ["Thor","Superman"];

var filtered = heroes.filter(function(item) {
        return stars .indexOf(item.name) !== -1 ;
});

console.log(filtered);

edited Jun 10, 2018 at 13:59

answered Jun 10, 2018 at 13:47

Sajeetharan

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7 Comments

31piy Over a year ago

>= 0 is > -1.

31piy Over a year ago

Because the OP's code is working correctly. Please see the snippet. This question should be closed as off-topic.

Sajeetharan Over a year ago

but he has mentioned it returns undefined

31piy Over a year ago

I understand, but for clarification, a comment would have sufficed.

Slyper Over a year ago

Same question, I am not sure why @31piy down-voted my question as well ? People ask questions, because they are not sure about their code. This is wrong use of a down-vote.

|

Eddie · Accepted Answer · 2018-06-10 13:46:24Z

0

You can use includes to determine whether an array includes a certain element

var heroes = [{name:"Batman",franchise:"DC"},{name:"Ironman",franchise:"Marvel"},{name:"Thor",franchise:"Marvel"},{name:"Superman",franchise:"DC"}];
var stars = ["Thor", "Superman"];

var marvelHeroes = heroes.filter(function(hero) {
  return stars.includes(hero.name);
});

console.log(marvelHeroes);

For shorter code:

var heroes = [{name:"Batman",franchise:"DC"},{name:"Ironman",franchise:"Marvel"},{name:"Thor",franchise:"Marvel"},{name:"Superman",franchise:"DC"}]
var stars = ["Thor", "Superman"];

var marvelHeroes = heroes.filter(o => stars.includes(o.name));

console.log( marvelHeroes );

Doc: includes()

answered Jun 10, 2018 at 13:46

Eddie

26.8k6 gold badges39 silver badges59 bronze badges

3 Comments

Slyper Over a year ago

Thanks @Eddie, From a performance point of view, which one is faster ? 'indexof' or 'includes'. My array is huge so performance is important.

Eddie Over a year ago

I like using includes() because it clearer Im not sure about the performance though.

Slyper Over a year ago

Hey @Eddie, I didn't down-voted, I think its 31piy, who down-voted my question initially, as well as all the answers. See the conversation in Sajeetharan's reply above.

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