Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Using parentNode to Traverse Up the DOM

Posted by joeboo2529
joeboo2529
9,805 Points

does anyone know how to select nested ul/ol list by using getElementByTag name then count how many nested ul/ol inside? 

<ul>
        <li>Item:
            <ol><!--level 1-->
                <li>Point:
                    <div>
                        <ul><!--level 2-->
                            <li>elem1</li>
                        </ul>
                    </div>
                </li>
            </ol>
        </li>
        <li>elem2</li>
    </ul>



    <ul>
        <li>simple list1</li>
    </ul>

    <ul>
    </ul>

2 Answers

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

Sure, you nearly described the process yourself in the question.

var ul = document.getElementsByClassName("ul")[0];
var nested = ul.getElementsByTagName("OL").length
           + ul.getElementsByTagName("UL").length;
alert(`There are ${nested} nested lists inside the outer one.`);
joeboo2529
joeboo2529
9,805 Points

sorry I didn't explain properly. What I meant to say was - I'm trying to select the "UL" tag try to count the length of nested ul/ol inside. It should return 2.

I've tried to loop through the "li" but not too sure how? hope that make sense.

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

That's exactly what the code shown does. It selects the outer "ul" and then counts the nested lists inside, putting the count into the variable "nested". The alert then confirms that value is 2.

joeboo2529
joeboo2529
9,805 Points
joeboo2529
joeboo2529
9,805 Points

Steven Parker thank you for such a simple solution, but just a quick question. Don't you need to loop through the "<li>" tag first and check what is inside? e.g dom traversing etc?

Thank you in advance.

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

You don't need a program loop because getElementsByTagName handles finding all the elements for you.