Javascript function to 'get element by parent class' and assign

function myFunction(element){
  liArray = document.getElementById("leftlist").childNodes;
  i=0;
  while(liArray[i]){
    liArray[i].id="";
    i++;
  }
  element.id="current";  // or element.className  ?
}

/**** css *********/
ul#leftlist {background-color: rgb(205,205,205);}
ul#leftlist li#current  a{color: rgb(96,176,255);  background-color:218,218,218);}
ul#leftlist li a{ color: rgb(86,86,86);}
#leftlist a:link{color: rgb(86,86,86);background-color: #ddd;}
#leftlist a:active{color: rgb(96,176,255); background-color: rgb(218,218,218); }

/****** html *********/
<ul id="leftlist">
  <li onClick='myFunction(this);'><a href="123" bla bla </a></li>
  <li onClick='myFunction(this);'> .... etc.</li>
</ul>

ul#leftlist li.current a {
  color: rgb(96,176,255) !important;
  background-color:218,218,218) !important;
}

ul#leftlist li#current  a{color: rgb(96,176,255);  background-color:218,218,218);}

ul#leftlist li#current  a{color: rgb(96,176,255);  background-color: rgb(218,218,218);}

liArray=element.parentNode.getElementsByTagName("li");

function myFunction(element){
  var liArray = document.getElementById("leftlist").childNodes;
  var i=0, item;
  while (item = liArray[i++]) {
    if (item.nodeType === 1) {
      item.className = item.className.replace(/(^| )current( |$)/g, '');
    }
  }
  element.className += " current";
}

ul#leftlist li.current a { ... }