[html] Show an image preview before upload

In my HTML form I have input filed with type file for example :

 <input type="file" multiple>

Then I'm selecting multiple files by clicking that input button. Now I want to show preview of selected images before submitting form . How to do that in HTML 5?

Here I did with jQuery using FileReader API.

Html Markup:

<input id="fileUpload" type="file" multiple />
<div id="image-holder"></div>

jQuery:

Here in jQuery code,first I check for file extension. i.e valid image file to be processed, then will check whether the browser support FileReader API is yes then only processed else display respected message

$("#fileUpload").on('change', function () {

     //Get count of selected files
     var countFiles = $(this)[0].files.length;

     var imgPath = $(this)[0].value;
     var extn = imgPath.substring(imgPath.lastIndexOf('.') + 1).toLowerCase();
     var image_holder = $("#image-holder");
     image_holder.empty();

     if (extn == "gif" || extn == "png" || extn == "jpg" || extn == "jpeg") {
         if (typeof (FileReader) != "undefined") {

             //loop for each file selected for uploaded.
             for (var i = 0; i < countFiles; i++) {

                 var reader = new FileReader();
                 reader.onload = function (e) {
                     $("<img />", {
                         "src": e.target.result,
                             "class": "thumb-image"
                     }).appendTo(image_holder);
                 }

                 image_holder.show();
                 reader.readAsDataURL($(this)[0].files[i]);
             }

         } else {
             alert("This browser does not support FileReader.");
         }
     } else {
         alert("Pls select only images");
     }
 });

Detailed Article: How to Preview Image before upload it, jQuery, HTML5 FileReader() with Live Demo

For background images, make sure to use url()

node.backgroundImage = 'url(' + e.target.result + ')';

Without FileReader, we can use URL.createObjectURL method to get the DOMString that represents the object ( our image file ).

Don't forget to validate image extension.

<input type="file" id="files" multiple />
<div class="image-preview"></div>

let file_input = document.querySelector('#files');
let image_preview = document.querySelector('.image-preview');

const handle_file_preview = (e) => {
  let files = e.target.files;
  let length = files.length;

  for(let i = 0; i < length; i++) {
      let image = document.createElement('img');
      // use the DOMstring for source
      image.src = window.URL.createObjectURL(files[i]);
      image_preview.appendChild(image);
  }
}

file_input.addEventListener('change', handle_file_preview);