I would like to save my map as the .png image. I've managed to do so with the code below. Unfortunately, it looks like something is missing, as I cannot save it under the custom name.

document.getElementById('export-png').addEventListener('click', function () {
  map.once('rendercomplete', function () {
  var mapCanvas = document.createElement('canvas');
  var size = map.getSize();
  mapCanvas.width = size[0];
  mapCanvas.height = size[1];
  var mapContext = mapCanvas.getContext('2d');
  Array.prototype.forEach.call(
  document.querySelectorAll('.ol-layer canvas'),
  function (canvas) {
    if (canvas.width > 0) {
      var opacity = canvas.parentNode.style.opacity;
      mapContext.globalAlpha = opacity === '' ? 1 : Number(opacity);
      var transform = canvas.style.transform;
      // Get the transform parameters from the style's transform matrix
      var matrix = transform
        .match(/^matrix\(([^\(]*)\)$/)[1]
        .split(',')
        .map(Number);
      // Apply the transform to the export map context
      CanvasRenderingContext2D.prototype.setTransform.apply(
        mapContext,
        matrix
      );
      mapContext.drawImage(canvas, 0, 0);
    }
  }
 );
 if (navigator.msSaveBlob) {
   // link download attribuute does not work on MS browsers
   var imgName = prompt("Please provide the name", "survey_map");
   navigator.msSaveBlob(mapCanvas.msToBlob(), imgName + '.png');
 } else {
   var link = document.getElementById('image-download');
   link.href = mapCanvas.toDataURL();
   link.click();
 }
});
 map.renderSync();
 });

I used the prompt property, but it looks like it doesn't work here.

Is it possible to set the custom name for this png image?