es6 嵌套数组循环,JS（ES6）：根据嵌套数组属性过滤数组

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?

解决方案

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'))