js怎么获取背景图片呢?用这个返回的是空,不知道是怎么回事

console.log(document.getElementById("mainnav").style)document.getElementById("id").style.backgroundImagebackground获取

解决方案 »

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写在样式表里的样式是没办法直接用style来获取的，，具体的可以自己百度一下currentStyle跟getComputedStyle。
通过dom的stlye属性或者jquery的$().css(background)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
div{
width:400px;
height:400px;
background-image:url(1.jpg);
background-repeat:no-repeat;
background-color:#933;
background-position:center;
}
</style>
<script type="text/javascript">
function init(){
var a=document.getElementById("test");
var style="";
if(document.defaultView&&document.defaultView.getComputedStyle){
style=document.defaultView.getComputedStyle(a);
}else{
style=a.currentStyle;
}
alert(style.backgroundImage);
}
window.onload=init;
</script>
</head><body>
<div id="test"></div>
</body>
</html>
类似这样试试
我想实现的是利用img图片加载来显示网页的加载状态百分比貌似有点问题,背景的没有用上,
这是代码,以后再完善下
(function( window, undefined ) {});
var class2type = {},tmp=[],
core_toString = class2type.toString,
core_push   = class2type.push;
Array.prototype.del = function() {
var a = {}, c = [], l = this.length;
for (var i = 0; i < l; i++) {
  var b = this[i].src||this[i];
  var d = (typeof b) + b;
  if (a[d] === undefined) {
c.push(this[i]);
a[d] = 1;
  }
}
return c;
}  var pageload={set:{class:"*",color:"red"},
type: function( obj ) {
if ( obj == null ) {return String( obj );}
return typeof obj === "object" || typeof obj === "function" ? class2type[ core_toString.call(obj) ] || "object" : typeof obj;
},
isFunction: function( obj ) {return this.type(obj) === "function";},isArray: Array.isArray || function( obj ) {return this.type(obj) === "array";},isWindow: function( obj ) {return obj != null && obj == obj.window;},isNumeric: function( obj ) {return !isNaN( parseFloat(obj) ) && isFinite( obj );},isArraylike:function ( obj ) { var length = obj.length,type = this.type( obj ); if ( this.isWindow( obj ) ) {return false;} if ( obj.nodeType === 1 && length ) { return true;} return type === "array" || type !== "function" && ( length === 0 || typeof length === "number" && length > 0 && ( length - 1 ) in obj );
},
makeArray:function(a,b){
var list=b||[];
if ( a != null ) {if ( this.isArraylike(Object(a)) ) { this.merge(list, typeof a === "string" ? [ a ] : a );} else { core_push.call( list, a ); }}
return list;
},
merge: function( first, second ) {
var l = second.length,
i = first.length,
j = 0; if ( typeof l === "number" ) {
for ( ; j < l; j++ ) {
first[ i++ ] = second[ j ];
}
} else {
while ( second[j] !== undefined ) {
first[ i++ ] = second[ j++ ];
}
} first.length = i; return first;
},
getStyles : function( elem ) { try{
if(window.getComputedStyle)
return window.getComputedStyle( elem, null );
else alert("err")
}catch(e){alert("aa")}
},
byClass: function(sClass, oParent) {
var aClass = [],tm,imgobj;
var reClass = new RegExp("(^| )" + sClass + "( |$)");
var aElem = this.byTagName("*", oParent);
for (var i = 0; i < aElem.length; i++) {
if(reClass.test(aElem[i].className) && this.getStyles(aElem[i]).backgroundImage!=="none" ){
tm=this.getStyles(aElem[i]).backgroundImage.replace(/url$[\"\']?/g,"").replace(/[\"\']?$/g,"");
imgobj=new Image();
imgobj.src=tm;aClass.push(imgobj);
}
//reClass.test(aElem[i].className) && aClass.push(aElem[i]);
}
return aClass
},
byTagName: function(elem, obj) {
var list=[];
return this.makeArray((obj || document).getElementsByTagName(elem),list)
},
creatPageLoad:function(){
var div=document.createElement("div");
div.id="pageLoad";
div.style.height=3;
div.style.position="absolute";
div.style.backgroundColor=this.set.color;
div.style.top=0;div.style.zIndex=100;
document.body.appendChild(div);
return div;
},show:function(num,obj){
var tmp=obj.style.width;
var sss2=document.getElementById("sss2")
sss2.innerHTML=obj.style.width;
obj.style.width=((num*100)>=1?100:(num*100).toFixed(2))+"%";
//console.log('3.'+obj.style.width)
//if(num>=1)this.hide(obj)
},
hide:function(obj){ obj.style.display="none";},
init:function(){
var imglist,sums=0,wh=0,_this=this;imglist=_this.byTagName("img"),j=0;
var sss=document.getElementById("sss");
var sss2=document.getElementById("sss2");
imglist=_this.makeArray(_this.byClass(_this.set.class),imglist); imglist=imglist.del();
var pageLoad=pageLoad||_this.creatPageLoad();
for(var i=0;i<imglist.length;i++){
// if(imglist[i].width||imglist[i].height){
try{
if(imglist[i].complete) {
console.log('1.'+(imglist[i].width||imglist[i].style.width||1)+','+imglist[i].height+','+sums+','+imglist[i].src)
}else{
console.log('2.'+(imglist[i].width||imglist[i].style.width||1)+','+imglist[i].height+','+sums+','+imglist[i].src) }}catch(e){alert("console.log error")}
sums+=(imglist[i].width*imglist[i].height);

}
//console.log('s'+wh+','+sums);
for(var i=0;i<imglist.length;i++){
//document.write(imglist[i].src+','+ imglist[i].width*imglist[i].height+'<br>');

if(imglist[i].complete) {
wh+=(imglist[i].width*imglist[i].height);
//console.log('1.'+wh/sums)
_this.show(wh/sums,pageLoad);
}else{
imglist[i].onload=function(){
wh+=(this.width*this.height);
//console.log(((wh/sums*100).toFixed(2))+','+''+''+this.width+','+this.height)
_this.show(wh/sums,pageLoad);
//if(wh/sums>=1)console.log(sums);
this.onload=null;
}
}
}
//console.log(wh+','+sums) tmp=imglist;
//document.write(imglist.length);
}
}
window.pl=pageload;
pl.fn=pl.prototype;pl.init();
//document.write(pl.byTagName("img").length)