如何过滤 arrays 的数组并只返回每个内部数组的一部分？

Question

I have the following array of arrays:

const myArray = [ ['1', 'first'], ['2', 'second'], ['3', 'third'], ['4', 'fourth'] ]

I want to return an array like:

[ 'first', 'second', 'third', 'fourth' ]

I'm trying the following filter:

const res = myArray.filter( elm => elm[1] )

but it doesn't return the desired filter, just return the same...

Answer 1

.filter() is used to create a subset of an array containing elements that pass a certain requirements test.

.map() is used create a new array consisting of the results of passing the elements through a function.

The following should work as you intend:

const res = myArray.map(elm => elm[1]);

Answer 2

When you call map on an array, it executes that callback on every element

within it, returning a new array with all of the values that the callback

returned.

Filter does exactly what it sounds like: It takes an array and filters out unwanted elements.

 const myArray = [ ['1', 'first'], ['2', 'second'], ['3', 'third'], ['4', 'fourth'] ] console.log(myArray.map(item=>item[1]))