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Why is there [0] in the line mentioned

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#1

Why is there [0] in line below
“const submenu = document.getElementsByClassName(“menu__sub”)[0];”

and why does the code doen’t work when we remove it.

#2

The [0] in the line const submenu = document.getElementsByClassName("menu__sub")[0]; is used to access the first element that matches the specified class name.

document.getElementsByClassName("menu__sub") returns a collection (a NodeList) of all elements with the class name “menu__sub.” This collection is similar to an array, but it doesn’t have all the array methods.

In this case, it appears that you expect there to be only one element with the class “menu__sub” on your page, so you use [0] to access that element in the collection.

I hope this helps. If you need further explanation, please let me know.
Thanks!

Regards!
Komal Arif
Sr. Developer Advocate at Educative