//***Free for use without any attribution
//***Originally posted by Nicke on #javascript
//***Cleaned up/changed by Gavin Kistner

/*********************************************************************************
Parameters:
	 frm          - a form object or the name of the form

	 excludeNames - a single string, array of strings, or space-delimited list
					specifying names of form elements NOT to include in the
					query string (optional)

	 preventCache - append a unique value to the end of the query string (opt)

Returns a string with the form's name/value pairs to be used as a query string

Examples:
  <form
      method="get"
      action="foo.html"
      onclick="location.href=this.action+'?'+BuildQueryString(this)">

  -or-

  location.href="foo.html?"+BuildQueryString('myForm',['hidden1','hidden2'],true);

**********************************************************************************/
 
function BuildQueryString(frm, excludeNames, preventCache ){
	if (typeof(frm)=="String") frm = document.forms[frm];
	if (frm==null || frm.elements==null) return;
	if (typeof(excludeNames)=="String") excludeNames=excludeNames.split(' ');
	if (excludeNames){
		for (var i=0,len=excludeNames.length;i<len;i++){
			excludeNames[excludeNames[i]]=true;
		}
	} else excludeNames={};
	var qs = '';
	var els = frm.elements;
	for (var i=0,len=els.length;i<len;i++){
		var el = els[i];
		if (!el.name || el.disabled || excludeNames[el.name] ||
		   ((el.type=="checkbox" || el.type=="radio") && !el.checked) ) continue;
		if (el.type=='select-multiple'){
			for (var j=0,len2=el.options.length;j<len;j++){
				var opt = el.options[j];
				if (opt.selected){
					qs+=el.name+'='+escape(opt.value?opt.value:opt.text)
					    +(j<(len2-1)?'&':'');
				}
			}
		} else qs+=el.name+'='+escape(el.value)+(i<(len-1)?'&':'');
	}
	if (preventCache) qs+=(qs.length>0?'&':'')+'nocache='+(new Date())*1;
	return qs;
} 

/**********************************************************************************
NOTE1: The name property of a form element is NOT escaped, just the value. 

NOTE2: Perhaps for historical reasons (in DOM Level 0, the image type
	   input element was not addressable as an object), you cannot reference an
	   image type input element through the Level 0 referencing scheme of
	   document.formName.inputName. Nor do these controls show up in the
	   collection returned by a form's elements property. The exception to this
	   is IE/Mac, which does allow such references, so dont use image input
	   type elements in your forms !!!
	   
NOTE3: Unlike using a real form, this script will return name/value for ALL 
       <input type="submit"> in your form, not just the one the user clicked on.
       With this script there is no way to determine which submit button the user
       used unless you handle the submission as an onclick event from the button
       itself and handle the query string specifically there.
**********************************************************************************/