Catching error in chained promises

promise-all.js

function fn1(previous) {
  console.log('previous: ' + previous, 'current: step1');
  return Promise.resolve('step1');
}

function fn2(previous) {
  console.log('previous: ' + previous, 'current: step2');
  return Promise.reject('step2');
}

function fn3(previous) {
  console.log('previous: ' + previous, 'current: step3');
  return Promise.resolve('step3');
}

function fn4(previous) {
  console.log('previous: ' + previous, 'current: step4');
  return Promise.resolve('step4');
}

let promiseList = [
	fn1(0), 
	fn2(0).catch(error => console.log('Error caught at ' + error + ' without stopping the chain')), 
	fn3(0)
];

Promise.all(promiseList)
	.then(result => { console.log(result); return fn4(1); })
	.catch(error => console.log('caught: ' + error));


// ----------------------------------------------------------------------------
// This will return the following output in the console
// 
//   previous: 0 current: step1
//   previous: 0 current: step2
//   previous: 0 current: step3
//   Error caught at step2 without stopping the chain
//   ["step1", undefined, "step3"]
//   previous: 1 current: step4
// 
// If you remove the .catch(error => console.log(...)), all concurrent promises 
// will be executed (even fn3()) but stops after : fn4 will never be called:
//   previous: 0 current: step1
//   previous: 0 current: step2
//   previous: 0 current: step3
//   caught: step2

promise.js

function fn1(previous) {
  console.log('previous: ' + previous, 'current: step1');
  return Promise.resolve('step1');
}

function fn2(previous) {
  console.log('previous: ' + previous, 'current: step2');
  return Promise.resolve('step2');
}

function fn3(previous) {
  console.log('previous: ' + previous, 'current: step3');
  return Promise.reject('step3');
}

function fn4(previous) {
  console.log('previous: ' + previous, 'current: step4');
  return Promise.resolve('step4');
}

fn1()
  .then(previous => fn2(previous))
  .then(previous => fn3(previous).catch(error => console.warn('error caught on ' + error)))
  .then(previous => fn4(previous))
  .catch(error => console.log('caught: ' + error));


// ----------------------------------------------------------------------------
// This will return the following output in the console:
// 
//   previous: undefined current: step1
//   previous: step1 current: step2
//   previous: step2 current: step3
//   error caught on step3
//   previous: undefined current: step4
//
// If you remove .catch(error => console.warn(error)), you will get:
// 
//   previous: undefined current: step1
//   previous: step1 current: step2
//   previous: step2 current: step3
//   caught: step3