filter array of object base on array of object

Question

This is my data

[{name:'james',grade:'A'},
{name:'john',grade:'B'},
{name:'iris',,grade:'A'},
{name:'ivan',,grade:'C'}]

I want to keep object that has grade A and C, it's easy I can just do filter like

person.filter(obj => obj.grade === 'A' || obj.grade === 'C')

but now I have an array of object.

[{grade:'A'},{grade:'C'}]

any clue how can I do filtering now? do I need nested loop?

Can you give an example of the data you're dealing with? Your question is unclear — Andrew Li
– Andrew Li, Commented May 25, 2017 at 6:30
@AndrewLi 'C' and 'A' is not string or value stored in any variable but array of object. — Giala Jefferson
– Giala Jefferson, Commented May 25, 2017 at 6:31
What's wrong with your current code? The way you've phrased your question implies it should work. It's confusing. — Andrew Li
– Andrew Li, Commented May 25, 2017 at 6:33

Mayank Shukla · Accepted Answer · 2017-05-25 06:55:56Z

1

Use Array.prototype.some:

let person = [{name:'james', grade:'A'},
              {name:'john', grade:'B'},
              {name:'iris', grade:'A'},
              {name:'ivan', grade:'C'}];

let predicate = [{grade:'A'},{grade:'C'}];
        
let result = person.filter(obj => predicate.some(p => p.grade == obj.grade))

console.log('result:', result)

If your predicate is more dynamic than that, compare all object properties instead of just p.grade.

person.filter(obj => predicate.some(p => {
    return Object.keys(p).every(k => obj[k] == p[k]);
}));

edited May 25, 2017 at 6:55

Mayank Shukla

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answered May 25, 2017 at 6:35

deceze♦

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6 Comments

Jeremy Thille Over a year ago

Your predicate is wrong, it doesn't include names. OP's output is weird, because it discards names for some reason, keeping only the grades.

deceze Over a year ago

No, predicate is OP's "but now I have an array of object". person is the first array which includes names. Edited to clarify.

Jeremy Thille Over a year ago

Oh damn, I think I just understood the question. I thought his filter was wrong, but actually he wants to reapply a second filter. Sorry

deceze Over a year ago

I can see where you fell off the wagon there… :)

Giala Jefferson Over a year ago

some is enough to do the job although I don't understand the second block of ur code.

|

Rahul Singh · Accepted Answer · 2017-05-25 06:40:31Z

0

Using underscore lib eg -

    var bbb = [
        {id: 839},
        {id: 854}
    ];
     var ids = {};
    _.each(bbb, function (bb) { ids[bb.id] = true; });

var data = [{grade:'A'},{grade:'C'}];
var value = {};
_.each(data , function (d) { value[data.garde] === 'A' | value[data.garde] === 'C' ; });

edited May 25, 2017 at 6:40

answered May 25, 2017 at 6:37

Rahul Singh

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3 Comments

RobG Over a year ago

Code-only answers aren't helpful. What is the OP's issue? How does your code fix it?

Rahul Singh Over a year ago

@JeremyThille i guess using libraries is makes the code cleaner i feel it purely optionaly i feel

Jeremy Thille Over a year ago

Yes sorry, I misunderstood OP's question. I de-downvoted your answer :)

marmeladze · Accepted Answer · 2017-05-25 06:41:08Z

0

Objects having grades A and C should be filtered as (classic js syntax),

var a = [
  {name:'james',grade:'A'},
  {name:'john',grade:'B'},
  {name:'iris',grade:'A'},
  {name:'ivan',grade:'C'}
];

a.filter(function(e) { 
  return (e.grade == 'A') || (e.grade == 'C');
});

answered May 25, 2017 at 6:41

marmeladze

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6 Comments

marmeladze Over a year ago

what's wrong with that answer? -)) missing semicolon? -))

Jeremy Thille Over a year ago

I made the same mistake, I misunderstood OP's question. His first filter works, but now he wants to apply a second filter based on predicate [{grade:'A'},{grade:'C'}]. His question is very misleading indeed. (I didn't downvote)

marmeladze Over a year ago

i dont really care about downvotes but I really didn't understand what he wants -))

Jeremy Thille Over a year ago

Well you don't come and help people on Stackoverflow to get downvoted, do you? :)

marmeladze Over a year ago

sure, but "sapere aude" outweighs such situations -))

|

Yury Tarabanko · Accepted Answer · 2017-05-25 06:43:23Z

0

If you have many grades to check (I don't know like all of them ;) ). You could first convert array into Set

const grades = new Set([{grade:'A'},{grade:'C'}].map(({grade}) => grade))

const persons = [{name:'james',grade:'A'},
  {name:'john',grade:'B'},
  {name:'iris',grade:'A'},
  {name:'ivan',grade:'C'}]

And then filter persons array using has

const filtered = persons.filter(({grade}) => grades.has(grade))

answered May 25, 2017 at 6:43

Yury Tarabanko

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1 Comment

Jaromanda X Over a year ago

surely this can be more generic, so that if user wants to also add a filter item {name:'john'} you wouldn't have to rewrite it :p (good answer though)

Nina Scholz · Accepted Answer · 2017-05-25 07:24:30Z

0

You could use a Set for the predicates and filter accordingly

let person = [{ name: 'james', grade: 'A' }, { name: 'john', grade: 'B' }, { name: 'iris', grade: 'A' }, { name: 'ivan', grade: 'C' }],
    predicate = [{ grade: 'A' }, { grade: 'C' }],
    result = person.filter((s => p => s.has(p.grade))(new Set(predicate.map(p => p.grade))));

console.log(result)

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered May 25, 2017 at 7:24

Nina Scholz

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