JSFiddle - React, Tailwind, and code Playground

JavaScript

$('body').append('<iframe id="upload"></iframe>');
var form = $('<form enctype="multipart/form-data" id="image_upload" action="index.php">'
     + '<input type="file" accept="image/*" multiple name="img[]" id="image" />'
     + '<br>'
     + '<input type="submit" value="Upload images" class="upload" />'
     + '</form>');

$('#upload').on('load', function() {
    $(this).contents().find('body').append(form);
});