Get the Children of an Element

To get the children of an element, you use the childNodes property of the element.

The following selects the children of the element whose id is container:

const container = document.querySelector('#container');
const children = container.childNodes;

How it works:

First, select the element whose id is container using the querySelector() method.
Then, use the childNodes property to get the children of the container elements.

To get the first and last children, you use the firstChild and lastChild properties as follows:

const container = document.querySelector('#container');

const firstChild = container.firstChild,
      lastChild = container.lastChild;

Source