RxJS in Devtools (Source Panel -> Snippet Tab -> Create a new Snippet)

RxSnippet.js

(async ()=>{

    let libUrl = 'https://unpkg.com/@reactivex/rxjs@6.3.3/dist/esm2015/index.js'; 
    // Change with your version
    let opUrl = 'https://unpkg.com/@reactivex/rxjs@6.3.3/dist/esm2015/operators/index.js';
    // Change with your version
    

    const Rx = await import(libUrl);
    const Op = await import(opUrl);

    /**
    * Write your RxJS code below, here a simple example
    */  
  
    const source$ = Rx.of(1, 2, 3, 4, 5);
    //output: 1,2,3,4,5
    const subscription = source$.pipe(
        Op.map(data => data*2),
        Op.filter(x => x <10))
       .subscribe(val => console.log(val));
    
})()