Question

Is there a way to change an attribute of a CSS class using javascript?

<style type="text/css">
  .fool select {
    display: block;
  }
</style>

<p class="fool">
  <select id="a" onchange="changeCSS()"> ... </select>
  <select id="b" > ... </select>
  <select id="c" > ... </select>
</p>

I want to change display:block to display:none for ALL <select> elements after a user call function changeCSS().

It looks simple but I can’t find a way to do this…

Answer 1

The key is to define extra rules for additional classes and add these classes to the elements rather than to rewrite the rules for a given style rule.

JS

function changeCSS() {
  var selects = document.getElementsByTagName("select");
  for(var i =0, il = selects.length;i<il;i++){
     selects[i].className += " hidden";
  }
}

CSS

.fool select.hidden, select.hidden {
   display: none;
}

Or for a really efficient method (but which might need a few more specific style rules too)

JS

function changeCSS() {
  document.getElementsByTagName("body")[0].className += " hideAllSelects"
}

CSS

body.hideAllSelects select {
   display: none;
}