IE6下CSS图片缓存问题

ie6下如果用css图片平铺，会出现cpu短暂100%的情况，主要原因在于，ie6会重复下载图片。

用一句代码即可搞定：

 

document.execCommand("BackgroundImageCache", false, true); 

当然为了其它浏览器上能正常通过，需要做下判断后调用，才更安全：

 

 

if(Browser.isIE6){
    try{
            document.execCommand("BackgroundImageCache", false, true);  
    }
    catch(e1){}
}

平台检测代码可以这样写，摘自Ext源码：

 

var Browser = {};
try{
    (function(){
        var idSeed = 0,
        ua = navigator.userAgent.toLowerCase(),
        check = function(r){
            return r.test(ua);
        },
        DOC = document,
        isStrict = DOC.compatMode == "CSS1Compat",
        isOpera = check(/opera/),
        isChrome = check(/\bchrome\b/),
        isWebKit = check(/webkit/),
        isSafari = !isChrome && check(/safari/),
        isSafari2 = isSafari && check(/applewebkit\/4/), // unique to Safari 2
        isSafari3 = isSafari && check(/version\/3/),
        isSafari4 = isSafari && check(/version\/4/),
        isIE = !isOpera && check(/msie/),
        isIE7 = isIE && check(/msie 7/),
        isIE8 = isIE && check(/msie 8/),
        isIE6 = isIE && !isIE7 && !isIE8,
        isGecko = !isWebKit && check(/gecko/),
        isGecko2 = isGecko && check(/rv:1\.8/),
        isGecko3 = isGecko && check(/rv:1\.9/),
        isBorderBox = isIE && !isStrict,
        isWindows = check(/windows|win32/),
        isMac = check(/macintosh|mac os x/),
        isAir = check(/adobeair/),
        isLinux = check(/linux/),
        isIpad = check(/ipad/),
        isSecure = /^https/i.test(window.location.protocol);
        extend(Browser,{
            isOpera:isOpera,
            isIE:isIE,
            isIE6:isIE6,
            isFirefox:isGecko,
            isSafari:isSafari,
            isChrome:isChrome,
            isIpad:isIpad
        });
    })();
}catch(e){}

 

 

//上面extend方法也很easy

 

 

function extend(obj1,obj2){
    for(var o in obj2){
        obj1[o] = obj2[o];
    }
    return obj1;
}