previewImageFromInput.js

function previewImage(input, previewSelector) {
  if (input.files && input.files[0]) {
    var reader = new FileReader();
    
    reader.onload = function(e) {
      $(previewSelector).attr('src', e.target.result);
    }
    
    reader.readAsDataURL(input.files[0]);
  }
}