Get Siblings of an Element

This snippet gets the next sibling and previous sibling of an element, using the element.nextSibling and element.previousSibling properties.

const previous = element.previousSibling;
const next = element.nextSibling;

The following helper function gets all the following sibling of an element:

const getNextSiblings = (e) => {
    let siblings = [];
    while (e = e.nextSibling) {
        siblings.push(e);
    }
    return siblings;
}

And the following helper function gets all the previous siblings of an element:

const getPreviousSiblings = (e) => {
    let siblings = [];
    while (e = e.previousSibling) {
        siblings.push(e);
    }
    return siblings;
}

The following helper function gets all siblings of an element:

const getSiblings = (e) => {
    let siblings = [];

    e = e.parentNode.firstChild;
    do {
        siblings.push(e);
    } while (e = e.nextSibling);

    return siblings;
}

You can add a filter function to the helper function as shown in the following example:

const getSiblings = (e, filter) => {
    let siblings = [];

    e = e.parentNode.firstChild;
    do {
        if (!filter || filter(e)) {
            siblings.push(e);
        }
    } while (e = e.nextSibling);

    return siblings;
}

The following example uses the getSiblings() helper function to get all the siblings of an anchor element, which are also anchor elements:

const e = document.querySelector('a.first');

let links = getSiblings(el, (e) => {
    e.nodeName.toLowerCase() === 'a';
});

Source

https://www.javascripttutorial.net/dom/traversing/get-siblings-of-an-element/