Determine whether a checkbox is checked or unchecked

Question

I have a jQuery "checkbox checked/unchecked" function that works well. This is a checkbox for turning a particular URL parameter on or off. But I believe this code could be written a lot tighter. Does anyone have any suggestions?

$('#mapControl').live('click', function(){ 
var thisUrl = $(location).attr('href');
if($(this).is(':checked')) {
 var lastFour = thisUrl.substr(thisUrl.length - 4);
 var param;
 if (lastFour == 'com/') {param='?mapControl=true'} else {param='&mapControl=true'}
 thisUrl=thisUrl+param;
} else {
 $('#urlParam').val(thisUrl);
 if (thisUrl.indexOf('?mapControl=true') >= 0){
 thisUrl=thisUrl.replace('?mapControl=true',''); 
 } else if (thisUrl.indexOf('&mapControl=true') >= 0){
 thisUrl=thisUrl.replace('&mapControl=true',''); 
 } 
}
$('#urlParam').val(thisUrl);
});

I was given some suggestions (because i erroneously posted on StackOverflow) and was asked to post my question here. So with the feedback I got - I ended up with this code.

 function getParam() {
 var n;
 var myUrl = window.location.href;
 var lastFour = myUrl.substr(myUrl.length - 4);
 if (lastFour == 'com/') {n='?'} else {n='&'}
 return n;
}
$('#mapControl').on('click', function(){ 
 var thisUrl = window.location.href;
 var urlParamObj = $('#urlParam');
 if(this.checked === true) {
 var lastFour = thisUrl.substr(thisUrl.length - 4);
 var param = getParam();
 thisUrl=thisUrl+param+'mapControl=true';
 } else {
 urlParamObj.val(thisUrl);
 thisUrl=thisUrl.replace('?mapControl=true','').replace('&mapControl=true',''); 
 }
 urlParamObj.val(thisUrl);
});

I think this is the tightest it could be and I can use the getParam function for other checkboxes.

Answer 1

This is tighter I think:

function addParameter( url , name , value )
{
 var justHostname = ( location.href == ( location.protocol + "//" + location.host + "/" ),
 separator = justHostname?"?":"&"
 return url + separator + encodeURIComponent(name) + "=" + encodeURIComponent(value);
}
$('#mapControl').on('click', function(){ 
 var url = window.location.href,
 urlParamObj = $('#urlParam');
 if(this.checked) 
 {
 url = addParameter( url , 'mapControl' , 'true' )
 } else {
 url = url.replace('?mapControl=true&','?')
 .replace('?mapControl=true','')
 .replace('&mapControl=true',''); 
 }
 urlParamObj.val(thisUrl);
});

I did not test this, but you should catch the drift.

If it were me though, I would not re-invent the wheel and use the code from the answer here : https://stackoverflow.com/questions/6953944/how-to-add-parameters-to-a-url-that-already-contains-other-parameters-and-maybe