JavaScript / jQuery：测试窗口是否具有焦点

Question

如何测试浏览器是否具有焦点？

Answer 1

HTML：<button id="clear">clear log</button><div id="event"></div>使用Javascript：$(function(){&nbsp; &nbsp; $hasFocus = false;&nbsp; &nbsp; $('#clear').bind('click', function() { $('#event').empty(); });&nbsp; &nbsp; $(window)&nbsp; &nbsp; &nbsp; &nbsp; .bind('focus', function(ev){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $hasFocus = true;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $('#event').append('<div>'+(new Date()).getTime()+' focus</div>');&nbsp; &nbsp; &nbsp; &nbsp; })&nbsp; &nbsp; &nbsp; &nbsp; .bind('blur', function(ev){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $hasFocus = false;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $('#event').append('<div>'+(new Date()).getTime()+' blur</div>');&nbsp; &nbsp; &nbsp; &nbsp; })&nbsp; &nbsp; &nbsp; &nbsp; .trigger('focus');&nbsp; &nbsp; setInterval(function() {&nbsp; &nbsp; &nbsp; &nbsp; $('#event').append('<div>'+(new Date()).getTime()+' has focus '+($hasFocus ? 'yes' : 'no')+'</div>');&nbsp; &nbsp; }, 1000);});