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Editorial Team
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Asked: 2026-05-29T10:47:30+00:00

This is my HTML Code <html> <head> <title> Test Page </title> <script type=’text/javascript’> function

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This is my HTML Code

<html> 
  <head>
     <title> Test Page </title>
     <script type='text/javascript'>
        function test() {
           var ta = document.getElementsByTagName('body')[0].getElementsByTagName('li');
        }
     </script>
  </head>
  <body onload='test()'>
     <ul>
        <li> Test 1 </li>
        <li> Test 1 </li>
        <li> Test 1 </li>
        <li> Test 1 </li>
     </ul>
  </body>
</html>

Which of the following is better and why?

document.getElementsByTagName('body')[0].getElementsByTagName('li')

document.getElementsByTagName('li')

Also I couldn’t find any documentation or reference for getElementsByTagName implementation across browsers [atleast a overview on some major browsers] although I found really interesting things about document.getElementById that it is kind of hash look up atleast in firefox and chrome. Wish to have some help on the implementation too.

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1 Answer

  1. Editorial Team

    First of all, you should never get the body tag with this:

    document.getElementsByTagName('body')[0]

    It’s always more efficient to just use the built-in property for the body:

    document.body

    Second of all, all performance questions should be answered by testing with a tool like jsPerf. In this case, you can build a test that compares between these two if you want, but I think the point is moot given the previous simplification:

    document.getElementsByTagName("li")

    and

    document.body.getElementsByTagName("li")

    In a jsPerf I built to test this, document.getElementsByTagName('li') is the fastest, followed by document.body.getElementsByTagName('li') and document.getElementsByTagName('body')[0].getElementsByTagName('li') is the slowest.

    Here’s a screenshot of the test from several browsers:

    enter image description here

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