Finding descendants of elements in JavaScript

Задание 1

Given the element #elem:

html<ul id="elem">
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
</ul>

Find the first child of this element and make its text red.

Задание 2

Given the element #elem:

html<ul id="elem">
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
</ul>

Find the last child of this element and make its text red.

Задание 3

Given the element #elem:

html<ul id="elem">
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
  <li>text</li>
</ul>

Find all the children of this element and append the text '!' to the end of them.