// check all checkboxes
// to use: name="id[]" onclick="checkUncheckAll(this);"
function checkUncheckAll(theElement) {
	var theForm = theElement.form, i=0;
	for(i=0; i<theForm.length; i++){
		if(theForm[i].type == 'checkbox' && theForm[i].name != 'checkall'){
			theForm[i].checked = theElement.checked;
		}
	}
}

// specific check/uncheck functions
// to use: onclick="uncheckAll(this.form.elements['id[]'])"
function checkAll(field) {
	for(var i=0; i<field.length; i++) {
		field[i].checked = true;
	}
}
function uncheckAll(field) {
	for(var i=0; i<field.length; i++) {
		field[i].checked = false;
	}
}

// testing
// to use: <input type="button" value="Select all" onClick="selectAll(true);" />
function selectAll(state) {
	for(i=0; i<document.form.elements.length; i++) {
		var checkbox = document.form.elements[i];
		checkbox.checked = state;
	}
}