Q promises single error catcher

single-err-catcher.js

var Q = require('q');

function delaydo(x) {
	var deferred = Q.defer();
	setTimeout(function() {
		if (x === 2) {
			console.log("reject: "+x);
			deferred.reject(x);
		}
		else {
			console.log("resolve: "+x);
			deferred.resolve(x);
		}
	}, 1000);
	return deferred.promise;
}

delaydo(1)
.then(function() {
	return delaydo(2);
})
.then(function() {
	return delaydo(3);
})
.then(function() {
	return delaydo(4);
})
.catch(function(err) {
	console.log("Caught err: "+err);
});

stdout

resolve: 1
reject: 2
Caught err: 2