silently failing promises https://plnkr.co/edit/EvXPqjzobbwejTJcSKJO?p=previe

javascript_promises_silent_fail.js

console.log('Don\'t nest promises with catch without knowing what you are doing!');

new Promise(function(resolve1, reject1){
  reject1('This is fine');
})
new Promise(function(resolve2, reject2){
  return new Promise(function(resolve2Inner, reject2Inner){
    reject2Inner('This is also fine');
  })
})

//////////////////////////////////////////////////////////////////////////////////
new Promise(function(resolve2, reject2){
  return new Promise(function(resolve2Inner, reject2Inner){
    reject2Inner('This would be fine');
  }).catch(function(){
     console.warn('If not caught without propagation');
  })
}).catch(function(){
  console.log('this will catch nothing')
})
//////////////////////////////////////////////////////////////////////////////////

new Promise(function(resolve2, reject2){
  return new Promise(function(resolve2Inner, reject2Inner){
    reject2Inner('So always make sure');
  }).catch(function(err){
    return Promise.reject(err);
  })
}).catch(function(err){
  throw new Error(err + 'to propagate errors to the top');
})