I have an array, which looks like this:
const persons = [
{
name: "Joe",
animals: [
{species: "dog", name: "Bolt"},
{species: "cat", name: "Billy"},
]
},
{
name: "Bob",
animals: [
{species: "dog", name: "Snoopy"}
]
}
];
Now I want to filter based on the species. For example: every person which has a cat, should be returned:
const result = [
{
name: "Joe",
animals: [
{species: "dog", name: "Bolt"},
{species: "cat", name: "Billy"},
]
}
];
I have tried with the the filter()
method like this:
const result = persons.filter(p => p.animals.filter(s => s.species === 'cat'))
But this doesn't return the desired result (it returns both persons).
How can I filter the array bases on an attribute of a nested array?
Your inner filter still returns a "truthy" value (empty array) for the dog person. Add .length
so that no results becomes 0
("falsey")
const result = persons.filter(p => p.animals.filter(s => s.species === 'cat').length)
Edit: Per comments and several other answers, since the goal is to get a truthy value from the inner loop, .some
would get the job done even better because it directly returns true if any items match.
const result = persons.filter(p => p.animals.some(s => s.species === 'cat'))
你可能想用一些'
persons.filter(p => p.animals.some(s => s.species === 'cat'))
const persons = [ { name: "Joe", animals: [ {species: "dog", name: "Bolt"}, {species: "cat", name: "Billy"}, ] }, { name: "Bob", animals: [ {species: "dog", name: "Snoopy"} ] } ]; Filter = function(arr, a){ return arr.filter(t=>t.animals.filter(y=>y.species==a).length>0); } console.log(Filter(persons, 'cat'))
You can use filter()
with some()
method to check if some of the objects in animals array has species == cat
.
const persons = [{"name":"Joe","animals":[{"species":"dog","name":"Bolt"},{"species":"cat","name":"Billy"}]},{"name":"Bob","animals":[{"species":"dog","name":"Snoopy"}]}] const result = persons.filter(({animals}) => { return animals.some(({species}) => species == 'cat') }) console.log(result)
This should do the trick
persons.filter((person) => {
return person.animals.filter((animal) => {
return animal.species === 'cat';
}).length > 0;
});
Add the check on length, as filter returns an array, not a boolean.
You havent checked against the length of the second filter.
Filer only includes results that return a true
value. So we need to provide the second filter with a way of returning true if it finds something. We can do that by saying, if the returned array is > 0
const persons = [ { name: "Joe", animals: [ {species: "dog", name: "Bolt"}, {species: "cat", name: "Billy"}, ] }, { name: "Bob", animals: [ {species: "dog", name: "Snoopy"} ] } ]; const filtered = persons.filter(p => p.animals.filter(a => a.species === "cat").length > 0) console.log(filtered)
This should work!
const result = persons.filter(person => {
let innerResult = person.animals.filter(animal => {
return animal.species === 'cat';
});
return innerResult.length > 0;
});
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