how to continue with $q.all() when some promises fail

Question

I have an array of promises and each promise calls http.get().

var items = ["URL1", "URL2", "URL3"];
var promises = [];
//on each URL in items array, I want to create a promise and call http.get
items.forEach(function(el){
    return promises.push($http.get(el)); 
});
var all = $q.all(promises);
all.then(function success(data){
    console.log(data);
}).catch(function(reason){
    console.log("reason is", reason);
});

what's happening in my case

URL2.get does not get resolved, and it immediately triggers the catch() in the $q.all. As a result of this failure all.then() never gets invoked.

what I want

I want all the promises to continue even if one of the promise is rejected.

I found a similar post but the solution suggests to use another angular pacakage called Kris Kowal's Q. so I'm wondering how can I achieve it without using external package?

Answer 1

a simple hack might be adding a catch block to promises that return null, and filtering the null results from you promise.all result, something like:

let items = ["URL1", "URL2", "URL3"]
  , promises = items.map(url => $http.get(url).catch(e => null))
  , all = $q.all(promises).then(data => data.filter(d => !!d))

all.then(data => {
  // do something with data
}).catch(e => {
  // some error action
})

same thing in ES5:

var  items = ["URL1", "URL2", "URL3"]
  , promises = items.map(function(url){
     return $http.get(url).catch(function(e){return null})
  })
  , all = $q.all(promises).then(function(data){
    return data.filter(function(d){return !!d}) // filter out empty, null results
  })

all.then(function(data){
  // do something with data
}).catch(function(e){
  // some error action
})