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Challenges and limitations with advanced selectors and the document.querySelectorAll() method

Yesterday, I wrote about how to get all direct descendants that match a test condition.

A substantial number of folks wrote to me asking why I would use the Array.filter() method with the Node.children property instead of using a nested selector with the document.querySelectorAll() method.

let tuna = document.querySelectorAll('#sandwiches > .tuna');

This absolutely works when…

  1. The parent element has a unique selector, and
  2. You want to filter child elements based on a CSS selector.

If the parent element doesn’t have a unique selector (as in, no ID), you can use the :scope pseudo-class (thanks to read Stefan for sharing this one with me!).

Here, :scope refers to the sandwiches element.

// This is silly, since the element obviously has an ID
// Just roll with it
let sandwiches = document.querySelector('#sandwiches');

// Here, :scope refers to the sandwiches element
let tuna = sandwiches.querySelectorAll(':scope > .tuna');

When you’re filtering with things that can be targeted with CSS, this works great. But what if your criteria is more elaborate?

For example, what if you wanted to exclude…

  • The third child element
  • Child elements with more than one nested element inside it
  • Child elements with a nested button

In those situations, the Array.from(NodeChildren).fitler() approach is, in my opinion, more robust, simpler, and in some cases, the only option.

// exclude the third child element
let noThirdChild = Array.from(sandwiches.children).filter(function (elem, index) {
	return elem.matches('.tuna') && index !== 2;

// exclude more than one nested elements
let noNestedElements = Array.from(sandwiches.children).filter(function (elem) {
	return elem.matches('.tuna') && elem.children.length < 2;

// exclude items with nested buttons
let noNestedButtons = Array.from(sandwiches.children).filter(function (elem) {
	return elem.matches('.tuna') && !elem.querySelector('button');