如何在不更改原始数组的情况下过滤嵌套数组？

Question

I would like to return both the inner and outer array such as the following: [[3],[4],[5]];

This does not work:

var arr = [[1],[2],[3],[4],[5]];

arr.filter(function(el){
    return el.filter(function(inner){
        return inner >= 3;
    });
});

This does not work either:

var arr = [[1],[2],[3],[4],[5]];

arr.map(function(el){
    return el.filter(function(inner){
        return inner >= 3;
    });
});

Answer 1

You can use array destructuring to get easy access to the inner array elements in the callback function:

 const array = [[1],[2],[3],[4],[5]]; const filtered = array.filter(([inner]) => inner >= 3); console.log(array); // original console.log(filtered); // filtered 

Answer 2

map() and filter() functions don't mutate the array, they return a new array with the resulting items.

In the code you show us you're not assigning the result anywhere, also, you're trying to compare an array with a number:

If you wanted to return the values inside of their wrapping arrays, you would do it like this:

var arr = [[1],[2],[3],[4],[5]];

var newArr = arr.filter(function(inner){
    return inner[0] >= 3;
});

// newArr = [[3], [4], [5]]

you don't need the map function if you're only filtering.