lazy.js

/*
// egghead playlist 
// https://egghead.io/courses/advanced-react-component-patterns
*/

let a = 0;

[...document.getElementsByClassName('w-100 pa1 tl mv0 flex flex-row items-center no-underline dark-gray h2')]
  .map((e) => e.innerText )
  .forEach((d) => 
    a+= (parseInt(d[0])*60 + parseInt(d[2])*10  + parseInt(d[3])  // all vids have less than 10min duration (m:ss) so...
  ));

console.log(`${parseInt(a/3600)}:${parseInt(a/60)}:${a%60}`);