wait until condition is met before resolving promise.

promise-when.js

// setup
var value = false;
setTimeout(function(){
  value = true;
}, 1998);


// code
function promiseWhen(condition, timeout){
  if(!timeout){
    timeout = 2000;
  }
  var done = Promise.defer();
  setTimeout(function(){
    done.reject();
  }, timeout);
  function loop(){
    if(condition()){
      return done.resolve();
    }
    setTimeout(loop,0);
  }
  setTimeout(loop,0);
  
  return done.promise;
}


// test case
promiseWhen(function(){
  return value === true;
}).then(function(){
  console.log('done');
}, function (){
  console.log('timeout');
});

If the timeout triggers, your loop keeps running.

If the timeout triggers, your loop keeps running.

Good spot, there's no early return.

There's room for improvement 👍