问JavaScript / jQuery:测试窗口是否具有焦点

EN

function focuschange(fclass) {
    var elems=['textOut','textFocus'];
    for (var i=0;i<elems.length;i++) {
        document.getElementById(elems[i]).
            setAttribute('class',fclass);
    }
}
window.addEventListener("blur",function(){focuschange('havnt')});
window.addEventListener("focus",function(){focuschange('have')});
focuschange('havnt');

.have                { background:#CFC; }
#textOut.have:after  { content:'';      }
.havnt               { background:#FCC; }
#textOut.havnt:after { content:' not';  }

<span id='textOut'>Have</span><span id='textFocus'> focus</span>

setInterval(function() {
    var fclass='havnt';
    if (document.hasFocus()) {
      fclass='have';
    };
    var elems=['textOut','textFocus'];
    for (var i=0;i<elems.length;i++) {
        document.getElementById(elems[i]).
            setAttribute('class',fclass);
    }
},100);

#textOut.have:after  { content:'';     }
#textOut.havnt:after { content:' not'; }
.have  { background:#CFC; }
.havnt { background:#FCC; }

<span id='textOut'>Have</span><span id='textFocus'> focus</span>

<button id="clear">clear log</button>
<div id="event"></div>​

$(function(){

    $hasFocus = false;

    $('#clear').bind('click', function() { $('#event').empty(); });

    $(window)
        .bind('focus', function(ev){
            $hasFocus = true;
            $('#event').append('<div>'+(new Date()).getTime()+' focus</div>');
        })
        .bind('blur', function(ev){
            $hasFocus = false;
            $('#event').append('<div>'+(new Date()).getTime()+' blur</div>');
        })
        .trigger('focus');

    setInterval(function() {
        $('#event').append('<div>'+(new Date()).getTime()+' has focus '+($hasFocus ? 'yes' : 'no')+'</div>');
    }, 1000);
});​