NodeJS Timeout a Promise if failed to complete in time

Question

How can I timeout a promise after certain amount of time? I know Q has a promise timeout, but I\'m using native NodeJS promises and they don\'t have .timeout function.

Answer 1

While maybe there's no support for a promise timeout, you could race promises:

var race = Promise.race([
  new Promise(function(resolve){
    setTimeout(function() { resolve('I did it'); }, 1000);
  }),
  new Promise(function(resolve, reject){
    setTimeout(function() { reject('Timed out'); }, 800);
  })
]);

race.then(function(data){
  console.log(data);
  }).catch(function(e){
  console.log(e);
  });

A generic Promise.timeout:

Promise.timeout = function(timeout, cb){
  return Promise.race([
  new Promise(cb),
  new Promise(function(resolve, reject){
    setTimeout(function() { reject('Timed out'); }, timeout);
  })
]);
}

Example:

    Promise.timeout = function(timeout, cb) {
      return Promise.race([
        new Promise(cb),
        new Promise(function(resolve, reject) {
          setTimeout(function() {
            reject('Timed out');
          }, timeout);
        })
      ]);
    }
    
    function delayedHello(cb){
      setTimeout(function(){
        cb('Hello');
        }, 1000);
      }
    
    Promise.timeout(800, delayedHello).then(function(data){
      console.log(data);
      }).catch(function(e){
      console.log(e);
      }); //delayedHello doesn't make it.

    Promise.timeout(1200, delayedHello).then(function(data){
      console.log(data);
      }).catch(function(e){
      console.log(e);
      }); //delayedHello makes it.

Might be a little bit costly, because you are actually creating 3 promises instead of 2. I think it's clearer this way though.

You might want to setup a promise instead of having the function construct it for you. This way you separate concerns and you are ultimately focused on racing your promise against a newly built promise that will reject at x miliseconds.

Promise.timeout = function(timeout, promise){
  return Promise.race([
  promise,
  new Promise(function(resolve, reject){
    setTimeout(function() { reject('Timed out'); }, timeout);
  })
]);
}

How to use:

var p = new Promise(function(resolve, reject){
    setTimeout(function() { resolve('Hello'); }, 1000);
});

Promise.timeout(800, p); //will be rejected, as the promise takes at least 1 sec.