jQuery CSS图像预加载程序

Posted 2021-02-26

jQuery.preloadCssImages = function(){
 
        var allImgs = [];//new array for all the image urls  
        var k = 0; //iterator for adding images
        var sheets = document.styleSheets;//array of stylesheets
 
        for(var i = 0; i<sheets .length; i++){//loop through each stylesheet
 
                var cssPile = '';//create large string of all css rules in sheet
                var csshref = (sheets[i].href) ? sheets[i].href : 'window.location.href';
                var baseURLarr = csshref.split('/');//split href at / to make array
 
                baseURLarr.pop();//remove file path from baseURL array
 
                var baseURL = baseURLarr.join('/');//create base url for the images in this sheet (css file's dir)
 
                if(baseURL!="") baseURL+='/'; //tack on a / if needed
 
                if(document.styleSheets[i].cssRules){//w3
 
                        var thisSheetRules = document.styleSheets[i].cssRules; //w3
 
                        for(var j = 0; j<thisSheetRules.length; j++){
                                cssPile+= thisSheetRules[j].cssText;
                        }
                }
                else {
                        cssPile+= document.styleSheets[i].cssText;
                }
 
                //parse cssPile for image urls and load them into the DOM
                var imgUrls = cssPile.match(/[^(]+.(gif|jpg|jpeg|png)/g);//reg ex to get a string of between a "(" and a ".filename"
 
                if(imgUrls != null && imgUrls.length>0 && imgUrls != ''){//loop array
 
                        var arr = jQuery.makeArray(imgUrls);//create array from regex obj        
 
                        jQuery(arr).each(function(){
                                allImgs[k] = new Image(); //new img obj
                                allImgs[k].src = (this[0] == '/' || this.match('http://')) ? this : baseURL + this;     //set src either absolute or rel to css dir
                                k++;
                        });
                }
        }//loop
        return allImgs;
}