使用JavaScript获得相当于“最大宽度：600像素”的CSS

您应该能够执行以下操作：

if (matchMedia) {
  var mq = window.matchMedia("(max-width: 600px)");
  mq.addListener(WidthChange);
  WidthChange(mq);
}

function WidthChange(mq) {
  if (mq.matches) { 
     //Window width is less than or equal to 600px
  } else { 
     //Window width is greater than 600px
  }
}