What happens if i reject / resolve multiple times in Kriskowal's q?
javascript, node.js, promise, q
Solution
Since promises can only resolve once (to either fulfilled or rejected), the first resolution wins and any further calls will be ignored. From the docs:
In all cases where a promise is resolved (i.e. either fulfilled or rejected), the resolution is permanent and cannot be reset. Attempting to call resolve, reject, or notify if promise is already resolved will be a no-op.
Should i avoid to call reject/resolve multiple times?
You can even design your application letting two methods "race" against each other to resolve a deferred, but in general it should be avoided to reduce confusion of a reader.
Problem
I'm studying the promises pattern and using kriskowal's q for node.js, having this snippet: ``` var deferred = Q.defer(); try { messageData = JSON.parse(message); } catch (e) { global.logger.warn('Error parsing JSON message.'); deferred.reject(e); } ... if (some_reason) deferred.resolve(something); ... return deferred.promise; ``` What if both the parser fails and some_reason is true? Will the execution procede from rejecting through resolving and both promise's method be called at different times, thus generating a bug? Should i avoid to call reject/resolve multiple times?