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JavaScript JavaScript and the DOM (Retiring) Making Changes to the DOM Appending Nodes

Marcos Gonzales
Marcos Gonzales
3,688 Points

Why are we using getElementsByTagName instead of querySelector? Is there a valid reason?

I am curious if there is a reason why because both of them work.

1 Answer

Jennifer Nordell
Jennifer Nordell
Treehouse Teacher

Hi there! You're correct that they both work. However, a querySelector is best used for really tricky selections of the DOM and getElementsBy... is better when used for simpler selections. The querySelector has a bit of additional parsing by the browser under the hood which can have a bit of a performance cost associated with it.

Here is a very simple jsperf test that I made where you can test the performance cost on a simple selection. You might also be interested in reading another discussion about this on this thread.

Hope this helps! :sparkles: