var url = 'https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=743446847,1016653021&fm=27&gp=0.jpg'
// 将链接地址字符内容转变成blob地址
fetch(url).then(res => res.blob()).then(blob => { 
// 创建隐藏的可下载链接   
var a = document.createElement('a');
a.style.display = 'none';
a.href = URL.createObjectURL(blob);       
a.download = 'QRcode.jpg';
document.body.appendChild(a);
a.click();
//移除元素
document.body.removeChild(a);
});