js如何下载图片到本地

$(function(){ 
 //二维码 
 (function(){ 
 var img_src = $('.qr_img')[0].src; 
 if(browserIsIe()){//假如是ie浏览器 
 $('.down_qr').on('click',function(){ 
 img_src = $('.qr_img')[0].src; 
 DownLoadReportIMG(img_src); 
 }); 
 }else{ 
 $('.down_qr').attr('download',img_src); 
 $('.down_qr').attr('href',img_src); 
 
 $('.sutmit_btn').on('click',function(){ 
 $('.down_qr').attr('download',img_src); 
 $('.down_qr').attr('href',img_src); 
 }); 
 } 
 
 })(); 
}); 
 
function DownLoadReportIMG(imgPathURL) { 
 //如果隐藏IFRAME不存在，则添加 
 if (!document.getElementById("IframeReportImg")) 
 $('<iframe style="display:none;" id="IframeReportImg" name="IframeReportImg" onload="DoSaveAsIMG();" width="0" height="0" src="about:blank"></iframe>').appendTo("body"); 
 if (document.all.IframeReportImg.src != imgPathURL) { 
 //加载图片 
 document.all.IframeReportImg.src = imgPathURL; 
 } 
 else { 
 //图片直接另存为 
 DoSaveAsIMG(); 
 } 
} 
function DoSaveAsIMG() { 
 if (document.all.IframeReportImg.src != "about:blank") 
 window.frames["IframeReportImg"].document.execCommand("SaveAs"); 
} 
//判断是否为ie浏览器 
function browserIsIe() { 
 if (!!window.ActiveXObject || "ActiveXObject" in window) 
 return true; 
 else 
 return false; 
}