Pass toDataUrl to image input of other function

I have some troubles passing dataurl value to another function in Javascript. By clicking on a link

    <a id="imageSaver" href="#">Save image</a> 

the canvas is converted toDataUrl

    var imageSaver = document.getElementById('imageSaver');
    imageSaver.addEventListener('click', saveImage, false);

    function saveImage(e) {
    this.href = canvas.toDataURL("image/jpg", 1.0);
    this.download = 'test.jpg'
    }

In my other function I have an upload button, that I want to replace with the image data that is created with click on "imageSaver". See the upload function of the second part:

    <input type="file" id="imageInput" accept="image/*" value="Bild hochladen">
    <a href="#" id="imageSelect">Foto hochladen</a> <br>
   window.onload = function(){
   var imageSelect = document.getElementById("imageSelect"),
   imageInput = document.getElementById("imageInput");  
   imageSelect.addEventListener("click", function (e) {
   imageInput.click();
   e.preventDefault();
   }, false);

  imageInput.addEventListener("change", function (e) {
  handleFiles(this.files);
  }, false);

Has anyone an Idea how to pass the data to the other function instead of the upload function?