javascript/typescript wait until condition meet

waitUntil.ts

// TypeScript/JavaScript 异步等待方法的实现
// refer to https://xmanyou.com/javascript-wait-until-condition-meet-or-timeout/
function waitUntil(condition:()=>boolean, timeout?:number, interval?:number) {
    if (timeout === void 0) { timeout = 0; } // if not set, wait forever
    if (interval === void 0) { interval = 50; } // default interval = 50ms
    let waitHandler;
    let timeoutHandler;
    return new Promise<void>(function (resolve, reject) {
        var waitFn = function () {
            if (condition()) {
              if(timeoutHandler){
                clearTimeout(timeoutHandler);
              }
              resolve();
            }
            else {
              waitHandler = setTimeout(waitFn, interval);
            }
        };
        // 
        waitHandler = setTimeout(waitFn, interval);

        // timeout, if timeout <=0, never timeout
        if(timeout>0){
          timeoutHandler = setTimeout(()=>{
            if(waitHandler){
              clearTimeout(waitHandler);
            }
  
            reject({
              code:"TIMEOUT",
              message: "timeout"
            });
          }, timeout);
        }
    });
}