如何使用Fabric.JS将计算机中的图像添加到已设置的图像后面？

<script src="fabric.js的链接地址"></script>

<canvas id="canvas"></canvas>

var canvas = new fabric.Canvas('canvas');

<input type="file" id="imageLoader" name="imageLoader">

document.getElementById('imageLoader').addEventListener('change', function (e) {
  var file = e.target.files[0];
  var reader = new FileReader();
  reader.onload = function (f) {
    var data = f.target.result;
    fabric.Image.fromURL(data, function (img) {
      canvas.add(img);
    });
  };
  reader.readAsDataURL(file);
});