gistfile1.txt

return redis.smembersAsync('langs')
.then(function(languages){
   // I need to call `articleExists('foo', language)` for each member of `languages`.
   // `articleExists` returns a promise; if it does, indeed, exist, then the promise resolves to
   //    the result I need (a name.)
   // if the article does *not* exist, then the promise returned by `articleExists` is rejected,
   //    and I need to move on to the next element of `languages`
}

return languages.reduceRight(function (next, language) {
    return function () {
        return articleExists("foo", language)
        .then(function () {
            return [name, language];
        }, function (error) {
            return next();
        });
    };
}, function () {
    throw Error("Can't find article");
})();

var results = [];
return redis.smembersAsync('langs')

.reduce(function(cur, language) {
    return cur.then(function(){
        return articleExists('foo', language);
    }).then(function(existResult) {
        results.push(existResult);
    }).catch(function(e) {});
}, Promise.resolve())

.thenReturn(results);

Procedural

var article = Promise.reject(new Promise.RejectionError("not found")); 
languages.forEach(function(lang) { 
    article = article.error(function(e) { return articleExists('foo', lang); }); 
}); 
return article;

Functional

return languages.reduce(function(article, lang) { 
    return article.error(function(e) { return articleExists('foo', lang); }); 
}, Promise.reject(new Promise.RejectionError("not found")));