how do we going to implement javascirpt inside the pug code example

Example: watch pug files

pug -w . -o ./html -P

// Note in the above command, the -w option stands for watch,
//the dot tells Pug to watch everything in the current directory,
//-o ./html tells Pug to output its HTML in the html directory and the
//-P option prettifies the output.

//The way this is going to work is that we’ll write our Pug code in index.pug
//and have the pug-cli watch this file for changes. When it detects any,
//it will take the contents of index.pug and render it as HTML
//in the html directory.