Javascript

https://stackoverflow.com/questions/43958335/select-folder-instead-of-single-file-input
https://stackoverflow.com/questions/14425007/get-metadata-of-local-mp3-file-using-html5-filesystem-api
https://stackoverflow.com/questions/3544898/what-does-a-colon-mean-within-an-html-id-attribute
https://stackoverflow.com/questions/441018/replacing-spaces-with-underscores-in-javascript
https://stackoverflow.com/questions/42526032/how-to-find-if-element-with-specific-id-exists-or-not/42526074
https://stackoverflow.com/questions/4250364/how-to-trim-a-file-extension-from-a-string-in-javascript
https://stackoverflow.com/questions/19331606/onclick-add-image-to-div
https://www.google.se/search?q=select+local+file+play+with+html5&oq=select+local+file+play+with+html5
Detect if HTML5 video is playing or paused and show or hide a Div accordingly
https://stackoverflow.com/questions/31307146/javascript-button-stop-all-audio-on-page
https://stackoverflow.com/questions/3623110/get-an-elements-id
https://www.google.com/search?q=javascript+store+data+inside+a+div&ie=utf-8&oe=utf-8&client=firefox-b
https://stackoverflow.com/questions/5785833/how-to-change-link-hrefs-via-javascript
Using files from web applications

Web development

SASS

apt install ruby-full rubygems autogen autoconf libtool make
gem install sass

Replacing jQuery with Vue
https://www.sitepoint.com/replacing-jquery-vue/

Google search “ajax jQuery send post to database”
https://www.google.com/search?q=ajax+jquery+send+post+to+database
* https://www.youtube.com/watch?v=gvGb5Z0yMFY