Javascript 如何降低CSS不透明度

我需要纯javascript函数来查找HTML元素的当前不透明度，并将其降低10%。是否有有效的跨浏览器解决方案

请不要使用像jQuery这样的JS框架（我有我的理由，所以不要问为什么），谢谢

我忘了，返回值可能需要手动强制转换成字符串。

使用IE变体

var style = document.getElementById(...).style;
if(browserIsIE) {
  var regExpResult = /alpha\(opacity\s*=\s*(\d*)\s*\)/.exec(style.filter);
  var opacity;
  if(regExpResult && regExpResult.constructor == Array && regExpResult[1] && opacity = parseInt(regExpResult[1])) {
    style.filter = "alpha(opacity = " + (opacity - 10) + ")";
  } else {
    style.filter = "alpha(opacity = 90)"; 
  }
} else {
  style.opacity = style.opacity=='' ? 0.9 : parseFloat(style.opacity)-0.1;
}

---

到目前为止，我已经取得了这一进展。你能测试一下吗

function normOpacity(num,ie) {
  num = parseFloat(num);
  if(num<0) return 0;
  if(num>1 && !ie) return 1;
  if(num>100 && ie) return 100;
  return num;
}

function changeOpacity(obj,diff) {
  if(!obj) return;
  if(!obj.filters) {
    var gcs = document.defaultView.getComputedStyle(obj,null);
    var op = parseFloat(gcs.getPropertyValue("opacity")) + diff;
    return obj.style.opacity = normOpacity(op)+"";
  }
  if(!obj.style.zoom) obj.style.zoom = 1;
  var op, al, dx = "DXImageTransform.Microsoft.";
  try { al = obj.filters.item(dx+"Alpha"); } catch(e) {}
  if(!al) try { al = obj.filters.item("Alpha"); } catch(e) {}
  if(!al) {
    var op = normOpacity(100+100*diff,true);
    return obj.style.filter+= "progid:"+dx+"Alpha(opacity="+op+")";
  }
  try { op = al["Opacity"]; } catch(e) { op = 100; }
  al["Opacity"] = normOpacity(parseInt(op)+100*diff,true)+"";
}

---

+1这是很有希望的，但是如果你破坏了其他过滤器，请看我的说明。他到现在还不在城里。

function normOpacity(num,ie) {
  num = parseFloat(num);
  if(num<0) return 0;
  if(num>1 && !ie) return 1;
  if(num>100 && ie) return 100;
  return num;
}

function changeOpacity(obj,diff) {
  if(!obj) return;
  if(!obj.filters) {
    var gcs = document.defaultView.getComputedStyle(obj,null);
    var op = parseFloat(gcs.getPropertyValue("opacity")) + diff;
    return obj.style.opacity = normOpacity(op)+"";
  }
  if(!obj.style.zoom) obj.style.zoom = 1;
  var op, al, dx = "DXImageTransform.Microsoft.";
  try { al = obj.filters.item(dx+"Alpha"); } catch(e) {}
  if(!al) try { al = obj.filters.item("Alpha"); } catch(e) {}
  if(!al) {
    var op = normOpacity(100+100*diff,true);
    return obj.style.filter+= "progid:"+dx+"Alpha(opacity="+op+")";
  }
  try { op = al["Opacity"]; } catch(e) { op = 100; }
  al["Opacity"] = normOpacity(parseInt(op)+100*diff,true)+"";
}

changeOpacity(obj,-0.1); // opacity should be 10% lower, regardless the browser