js: Promise Chaining

promiseChaining.js

myModule.validate = function(params){
	return new WinJS.Promise(function(ccb, ecb){
		myModule.preValidate(params).then(
			function prevalidateSuccess(result){
				ccb(result);
			}, 
			function prevalidateError(err){
				ecb(err);
			})
	});
}

/*
	Perform the preValidate
	Throw out any preValidate errors
	Throw out any validate errors
	Only continue if preValidate is successful
*/
myModule.validate = function(params){
	return myModule.preValidate(params)
		.then(function success(result){

		});
}


myModule.validate = function(params){
	return myModule.preValidate(params)
		.then(function success(result){
				
		}, function error(err){
			// Don't do both, do one or the other
			return err; // Goes to next 'normal' promise
			throw err; // Goes to next 'error' promise
		});
}

// Chaining some promises
myModule.validate = function(params){
	return myModule.preValidate(params)
		.then(function preValidateSuccess(result){
			// Return another promise
			return doSomethingAsync(result);
		})
		.then(function successSomethingAsync(something){
			// Do something and return
		});
}

// Errors are handled at the first available error pipeline
//  If the error promise returns, we go to next normal promise
// 	If the error throws, we go to the next error promise

myModule.validate(null).then(null, function error(err){
	// This would be the preValidate error, as this is the first error pipeline
});

// validObject is valid enough to pass preValidate, but internet is down or some other http error
myModule.validate(validObject).then(null, function error(err){
	// This would be the validate error if there were no internet connection for example
});



// Workblob example:

// Example promises
var getUserAsync = ()=> return user;
var getAddressAsync = ()=> return address;

var workblob = {}
workblob.inputObject = target

myApp.validate = function(workblob){
	return new WinJS.Promise(function(ccb, ecb){
		if(!workblob.target) return ecb(new Error("No Workblob target"));

		var getAndSavePromise = getUserAsync(workblob.target).then(function(user){
			// workblob.response.user = user;
			myApp.response.user = user;
			return workblob;
		});

		ccb(getAndSavePromise);
	});
}