Only add a slightly change to https://wordpress.org/plugins/easy-prism-syntax-highlighter/

• Download as zip
• Upload to your wordpress site and install

[code language="javascript"]
   function fun(){
    //stuff;
   }
[/code]

Follow the https://en.support.wordpress.com/code/posting-source-code/ standard [code].

So It could work with wordpress client Blogo :-)

[code javascript]
   function fun(){
    //stuff;
   }
[/code]

I haven't touch the code of GUI tinymce code editor, so the gui won't work.

All credits belong to the original author https://profiles.wordpress.org/cuamckuy/.