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Accessing Web Page Elements

By Stephen Bucaro

You can get access to a specific element on a webpage by assigning it a unique id and then using the document.getElementById method to create a reference to that element, as in the example is shown below.

<p id="accessme">You can access this text.</p>

<script language="JavaScript">
var bsize = 1;
function changeSize()
{
  var textref = document.getElementsById("accessme");
  if(bsize) textref.style.fontSize = "20px";
  else textref.style.fontSize = "12px";
  bsize = !bsize;
}
</script>

<input type="button" value="Change Text Size"
onclick="changeSize()"></input>

The example above changes the size of the text in the paragraph when you click on the button.

You may not be familiar with just creating a free-standing button that is not associated with a form. Actually, by default, it is associated with form[0] in the document's forms collection (assuming it's the first form on the webpage).

To access all elements of a certain type on a webpage, use the getElementsByTagName method to create a reference to the collection of all the elements of that type on the webpage, as in the example is shown below.

<p>You can access this text.</p>

<p>And this text.</p>

<p>And any other text in a paragraph.</p>

<script language="JavaScript">
var bsize = 1;
function changeSize()
{
  var coltext = document.getElementsByTagName("p");

  for(var i = 0; i < coltext.length; i++)
  {
    if(bsize) coltext[i].style.fontSize = "20px";
    else coltext[i].style.fontSize = "12px";
  }
  bsize = !bsize;
}
</script>

<input type="button" value="Change Text Size"
onclick="changeSize()"></input>

The example above changes the size of the text in all paragraphs when you click on the button.