function trim(sString){
    while (sString.substring(0,1) == ' ' || sString.substring(0,1) == '\n'){
        sString = sString.substring(1, sString.length);
    }
    while (sString.substring(sString.length-1, sString.length) == ' ' || sString.substring(sString.length-1, sString.length) == '\n'){
        sString = sString.substring(0,sString.length-1);
    }
    return sString;
}
function filterCities(){
    var anchor;
    var listitem;
    var cityContainer = document.getElementById('country_list');
    var filterString  = document.getElementById('apply_filter');
    if(trim(filterString.value)!=''){
        document.getElementById('remove_filter').disabled=false;
    }else{
        document.getElementById('remove_filter').disabled=true;
    }

    var i = 0;
    while(1){
        listitem = cityContainer.getElementsByTagName('li')[i];
        if(!listitem) break;
        anchor   = listitem.childNodes[0];
        if(anchor.childNodes[0].nodeType!=3){
            cityName = anchor.childNodes[0].childNodes[0].nodeValue;
        }else{
            cityName = anchor.childNodes[0].nodeValue;
        }
        if(cityName.toLowerCase().indexOf(filterString.value.toLowerCase())==-1){
            listitem.style.display='none';
        }else{
            listitem.style.display='list-item';
        }
        i++; 
        if(i>1000) break;
    } 
    
}

function clearFilterCities(){
    document.getElementById('apply_filter').value='';
    document.getElementById('remove_filter').disabled=true;
    var cityContainer = document.getElementById('country_list');
    var i = 0;
    while(1){
        listitem = cityContainer.getElementsByTagName('li')[i];
        if(!listitem) break;
        listitem.style.display='list-item';
        i++; 
        if(i>1000) break;
    } 
}