jQuery index() in vanilla javascript

Question

As per the jQuery api, the complementary operation to .get(), which accepts an index and returns a DOM node, .index() can take a DOM node and returns an index.

Answer 1

No loops needed, call Array#indexOf on .parentElement.children:

const element = document.querySelector('#baz');

[].indexOf.call(element.parentElement.children, element);
// => 2

You can even call it on a random list of elements, just like you can in jQuery:

const list = document.querySelectorAll('li');
const element = document.querySelector('#baz');

[].indexOf.call(list, element);
// => 2