JS前端下载图片

function download(link, filename){
  let a = document.createElement('a')
  a.href = link
  a.download = filename || 'default.png'
  a.dispatchEvent(new MouseEvent('click'))
}
let btn1 = document.querySelector('#btn1')
btn1.onclick = function(){
  download('images/test.gif', 'test.gif')
}