【JSリファレンス】Promise.withResolvers()

const {promise,resolve,reject} 
  = Promise.withResolvers( );

promise.then( console.log );

const time = 3000;

setTimeout( 
  ()=>resolve( `${time}ミリ秒待機しました`)
  ,time );

// 結果: 3000ミリ秒待機しました

document.addEventListener("DOMContentLoaded",()=>{
    
    document.getElementById("btn1")
      .addEventListener("click",()=>{
        resolve("btn1");
      });
    document.getElementById("btn2")
      .addEventListener("click",()=>{
        resolve("btn2");
      });

    const resetPromise = ()=>{
      ({promise,resolve,reject} 
            = Promise.withResolvers( ));
    };

    let promise,resolve,reject;
    resetPromise( );

    (async ()=>{
      while(true){
        const btn = await promise;
        switch(btn){
          case "btn1": 
            console.log("click btn1");break;
          case "btn2": 
            console.log("click btn2");break;
        }
        resetPromise();
      }
    })();
});