function getCookie( name ) {
    var start = document.cookie.indexOf( name + "=" );
    var len = start + name.length + 1;
    if ( ( !start ) && ( name != document.cookie.substring( 0, name.length ) ) ) {
        return null;
    }
    if(start == -1) return null;
    var end = document.cookie.indexOf( ";", len );
    if ( end == -1 ) end = document.cookie.length;
    return unescape( document.cookie.substring( len, end ) );
}
var COOKIE_EXPIRES = 0;
//expires：以天为单位
function setCookie( name, value, expires, path, domain, secure) {
    var today = new Date();
    today.setTime( today.getTime() );
    if ( expires ) {
        expires = expires * 1000 * 60 * 60 * 24;
    }else{
        expires = COOKIE_EXPIRES * 1000 * 60 * 60 * 24;
    }
    var expires_date = new Date( today.getTime() + (expires) );
    document.cookie = name+"="+escape( value ) +
        ( ( expires ) ? ";expires="+expires_date.toGMTString() : "" ) + 
        ( ( path ) ? ";path=" + (path||'/') :"") +
        ( ( domain ) ? ";domain=" + (domain||location.hostname) : '') +
        ( ( secure ) ? ";secure" : "" );
}

function deleteCookie( name, path, domain ) {
    if ( getCookie( name ) ) document.cookie = name + "=" +
            ( ( path ) ? ";path=" + path : ";path=" + '/') +
            ( ( domain ) ? ";domain=" + domain : "") +
            ";expires=Thu, 01-Jan-1970 00:00:01 GMT";
}