const promise = new Promise(function(resolve, reject){
  if (satisfiedCondition) {
    resolve('Task is done');
  } else {
    reject('Error occured');
  }
})

promise.then(function(data){
  console.log(data) // prints 'Task is done' when promise is resolved
}).catch(function(error){
  console.log(error) // prints 'Error occured' when promise is rejected
})