Commitment to provide the outcome of the second promise in case the first one encounters

I am trying to handle the scenario where I need to return the value of a second promise if the first one (value in cache) fails.

Below is my code snippet, but I'm encountering an issue where 'resolve' is not defined.

exports.getConfig = function (a, r) {
  return new Promise(resolve, reject)    {
    getConfigFromCache(a, r)
        .catch(function(e){
            getRouteConfigFromWeb(a, r)
        }).then(function(result) {
            //returning the value of the called promise
            resolve(result)
        })
  }
};

Assuming that both getConfigFromCache and getRouteConfigFromWeb functions correctly return promises, is there a way to achieve this or am I approaching it incorrectly?

javascriptpromisebluebird

Answer №1

No need to create a new Promise in this scenario:

exports.fetchConfig = function (param1, param2) {
    var cachedData = getConfigFromCache(param1, param2);
    return cachedData.catch(function(error) {
        return retrieveRouteConfigFromWeb(param1, param2);  // Note: returning *essential*
    });
}

If the call to getConfigFromCache() is successful, the resolved Promise should bypass the .catch and be returned directly.

In cases where the cache retrieval fails, the Promise from retrieveRouteConfigFromWeb() will be returned instead.

It's worth mentioning that the solution is hinted at in your initial question: "I want to return the result of a second promise if the first one (cached data) fails." - there was no actual return statement within the .catch block!

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