您可以这样做:

var flag = true;
function sendData() {
  html2canvas(document.getElementById('capture'), {
    allowTaint: false,
    useCORS: true
  }).then(function(canvas) {
    $('#testaroni').attr('src', function(index, src) {
      return 'https://cors-anywhere.herokuapp.com/' + src;
    });
    if(flag == true)
    {
        $('#test').attr('href', canvas.toDataURL('image/png'));
        $('#test').attr('download', 'Test.png');
        $('#test')[0].click();
        $('#testaroni').attr('src','https://cdn.bulbagarden.net/upload/thumb/4/49/Ash_Pikachu.png/250px-Ash_Pikachu.png');
        flag = false;
    }
  })
}