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

Marcos Gonzales
Marcos Gonzales
3,688 Points
Posted by 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
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STAFF
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Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
.a{fill-rule:evenodd;}techdegree
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: