如果 promise 没有返回值

Question

I have a promise that returns a function, the function does have its own error handling but sometimes for some reason this gets missed (need to explore this later).

I want to add a fallback that if the promise fails/null then return another function.

if (completedForm.isValid()) {
   return formDataQueue.push(formJson, this.company).then(function () {
      return self.trySync();
   });
}

Return self.trySync(): needs a error handler to assume it's not there as if it was commented out. My attempt does not seem to work.

if (completedForm.isValid()) {
   return formDataQueue.push(formJson, this.company).then(function () {
      //return self.trySync();
   }, function(error) {
      router.navigate('home');
   });
}

Answer 1

Have a look at the difference between .then(…).catch(…) and .then(…, …) .

To handle errors from trySync() (and only from there), you want to use

if (completedForm.isValid()) {
    return formDataQueue.push(formJson, this.company).then(function () {
        return self.trySync().catch(function(error) {
            router.navigate('home');
        });
    });
}