addClassName and removeClassName

Useful CSS Class handling functions.

Here I present addClassName, hasClass and removeClassName and also my old implementation of Array.indexOf. Since this is built into JS these days, you probably won't need it.

addClassName and removeClassName are useful functions because you can pass in space separated classNames and it will add/remove them all.

////////////////////////////////////////////////////////////////////////////////
//
// addClassName([object|string] oHTMLElement, string classNameToAdd)
//           Adds classNameToAdd to an HTMLElement. Guaranteed not to add the same className twice.
//           classNameToAdd can be a space separated list of classNames.
//           You can pass in the id to an object or the actual object
//
////////////////////////////////////////////////////////////////////////////////
function addClassName(oHTMLElement, classNameToAdd) {
  if (typeof(oHTMLElement)=="string")  { oHTMLElement = document.getElementById(oHTMLElement); }
  if (oHTMLElement) {
    var theClassName = oHTMLElement.className;
    if (theClassName && (theClassName.length > 0)) {  // If oHTMLElement already has a class name, some more work is needed
      var classNamesToAdd = classNameToAdd.split(" ");
      if (classNamesToAdd.length===1 && ((" " + theClassName + " ").lastIndexOf(" " + classNameToAdd + " ") === -1) ) { // If we only have one className to potentially add, take the "less work" approach
        oHTMLElement.className = oHTMLElement.className + " " + classNameToAdd;
      } else {
        var theClassNames = theClassName.split(" "),
            iEnd = classNamesToAdd.length,
            aClassName,
            theClassNamesToAddArray = [];
        for (var i=0;i<iEnd;i++) {
          aClassName = classNamesToAdd[i];
          if (theClassNames.indexOf(aClassName)===-1) {
            theClassNamesToAddArray.push( aClassName );
          }
        }
        oHTMLElement.className = oHTMLElement.className + " " + ((theClassNamesToAddArray.length > 1) ? theClassNamesToAddArray.join(" ") : theClassNamesToAddArray[0]);
      }
    } else {
      oHTMLElement.className = classNameToAdd;        // If oHTMLElement did not already have a class name, just add it
    }
  }
}

////////////////////////////////////////////////////////////////////////////////
//
// hasClassName([object|string] oHTMLElement, string classNameOfInterest)
//           Returns a boolean value of if an HTMLElement has the className of interest
//           You can pass in the id to an object or the actual object
//
////////////////////////////////////////////////////////////////////////////////
function hasClassName(oHTMLElement, classNameOfInterest) {
  return ((" " + oHTMLElement.className + " ").lastIndexOf(" " + classNameOfInterest + " ") > -1);
}
////////////////////////////////////////////////////////////////////////////////
//
// removeClassName([object|string] oHTMLElement, string classNameToRemove)
//           Removes classNameToRemove from an HTMLElement, if it exists.
//           classNameToRemove can be a space separated list of classNames.
//           You can pass in the id to oHTMLElement or the actual object
//
////////////////////////////////////////////////////////////////////////////////
function removeClassName(oHTMLElement, classNameToRemove) {
  if (typeof(oHTMLElement)=="string")  { oHTMLElement = document.getElementById(oHTMLElement); }
  if (oHTMLElement) {
    var theClassName = oHTMLElement.className;
    if (theClassName && (theClassName.length > 0)) {
      var theClassNameArray = theClassName.split(" "),
          classNamesToRemove = classNameToRemove.split(" "),
          iEnd = theClassNameArray.length,
          aClassName,
          theNewClassNameArray = [];
      for (var i=0;i<iEnd;i++) {
        aClassName = theClassNameArray[i];
        if (classNamesToRemove.indexOf(aClassName)===-1) {
          theNewClassNameArray.push( aClassName );
        }
      }
      switch (true) {
        case (theNewClassNameArray.length>1) :
          oHTMLElement.className = theNewClassNameArray.join(" ");
          break;
        case (theNewClassNameArray.length==1) :
          oHTMLElement.className = theNewClassNameArray[0];
          break;
        case (theNewClassNameArray.length==0) :
          oHTMLElement.className = "";
          break;
      }
    }
  }
}
////////////////////////////////////////////////////////////////////////////////
//
// Array.indexOf() - returns integer index where valueToSearchFor is in an Array
//
////////////////////////////////////////////////////////////////////////////////
if (Array.prototype.indexOf===undefined) {
  Array.prototype.indexOf = function( valueToSearchFor ) {
    var iEnd = this.length;
    var retVal = -1;
    for (var i=0;i<iEnd; i++) {
      if (this[i] == valueToSearchFor) {
        retVal = i;
        break;
      }
    }
    return retVal;
  };
}

by Shannon Norrell