使用.filter（）方法返回多个项目-JavaScript

Question

If I have an array with a set of numbers, and want to remove certain ones with the .filter method, I understand how to do this in when i need to remove a single item (or if i can use a mathematical expression), but can't get it to work with multiple items either purely by their value or position in the array.

In the following code I would like the new array selection to return the numbers 10, 12, 15

Also, I do need to do this with the filter() method only.

JS

let random = [4, 10, 12, 15, 30];
let selection = random.filter(function(num){

  return num === [10, 12, 30];

});

Answer 1

You can use includes :

 let random = [4, 10, 12, 15, 30, 10, 10, 12, 5]; let selection = random.filter(function(num){ var good = [10, 12, 30] return good.includes(num); }); console.log(selection) 

Of if you prefer the terseness of arrow function:

 let random = [4, 10, 12, 15, 30, 10, 10, 12, 5]; let selection = random.filter(num => [10, 12, 30].includes(num)) console.log(selection) 

Answer 2

Forgive me if I do not understand it correctly, but if what you're looking for is to filter an array by the item's index, you can use the second parameter passed to the filter method's callback, which is the index .

 let random = [4, 10, 12, 15, 30]; let selection = random.filter(function(num, index){ return index > 0 && index < 4; }); console.log(selection); 

Answer 3

You do need a condition that will return true or false when using filter, so the simplest way to do this with the filter method would be:

let random = [4, 10, 12, 15, 30];
let selection = random.filter(function(num){

if (num > 4 && num < 16) {return true};

});

The other way to do it would be filtering by position in the array and that would be better achieved with other array methods.

Answer 4

If I understand your question you want a function that takes a an array, checks if the elements are in your larger array and if they are there, removes them.

Filter might not be your best choice here because it doesn't alter the original array, it only makes a new array. Try using splice.

 let random = [4, 10, 12, 15, 30]; function remove(array) { for (var i = 0; i < array.length; i++) { if(random.includes(array[i])){ random.splice(random.indexOf(array[i]), 1) } } } remove([10, 12, 30]); console.log(random); // [4, 15] 

I am assuming you want to remove because if you already know which elements you want why filter them out? why not just pass them into your function as a new array? filter will create a new array anyways.

But if you would like to remove elements from your first array the answer above might help.