gen_async.js

function* asyncgen(userinput){
  let res= yield userinput;
  console.log(res); //print final result;
}
/** doasync() used to fake async task.
* @param: gen {function} generator function as input to be processed.
* @param: val {string} data to be passed.
*/
let doasync=(gen,val)=>{
   var getdata=gen(val);
   et data= getdata.next();

  setTimeout(()=>{

     if(data.value.includes('get'))getdata.next(data)

     else getdata.return(); //cancel all yields and process return and execute finally block if present.

  },3000);
}

doasync(asyncgen,'get-data');     // @returns {value: "get-data", done: false} after 3 seconds.
doasync(asyncgen,'cancel-data');  // @returns undefined as generator is returned.