I have a custom form in D8. Form has managed_file field. I am facing challenge regarding the limit of number of files upload to this field.
I have to make this managed_file field to upload only 3 images.
Can someone help me regarding this?
I can highly recommend DropzoneJS. It is a well maintained project, and will make it not only very easy for you to add a file upload widget with a specified max of files (or unlimited), it also provides a superior UX.
You can grab the module here: https://www.drupal.org/project/dropzonejs
Once you clone down the library from their GitHub repo, and enable the module, adding the form element is fairly straightforward:
$form['files_to_upload'] = [ '#type' => 'dropzonejs', '#title' => 'Add some files!', '#description' => 'Add your files here!', '#dropzone_description' => 'Drop the files in here, please!', '#max_filesize' => '50M', '#extensions' => 'png jpg zip', '#max_files' => '3', ];
When you submit, you'll have the temp files available to loop through and add to managed, or do as desired with the data:
There's a lot of neat functionalities that I'm not covering here. But, I've never regretted implementing this module, and it should hopefully help you out in your use case!