Add Resolve And Pass Multiple Values From A Then as a javascript til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_667 TILs and counting..._
+_668 TILs and counting..._
 
 ---
 
@@ -253,6 +253,7 @@ _667 TILs and counting..._
 - [Random Cannot Be Seeded](javascript/random-cannot-be-seeded.md)
 - [Reach Into An Object For Nested Data With Get](javascript/reach-into-an-object-for-nested-data-with-get.md)
 - [Render An Array Of Elements With React 16](javascript/render-an-array-of-elements-with-react-16.md)
+- [Resolve And Pass Multiple Values From A Then](javascript/resolve-and-pass-multiple-values-from-a-then.md)
 - [Running ES6 Specs With Mocha](javascript/running-es6-specs-with-mocha.md)
 - [Scoping Variables With A Block Statement](javascript/scoping-variables-with-a-block-statement.md)
 - [Splat Arguments To A Function](javascript/splat-arguments-to-a-function.md)

javascript/resolve-and-pass-multiple-values-from-a-then.md

@@ -0,0 +1,39 @@
+# Resolve And Pass Multiple Values From A Then
+
+Let's say you are chaining multiple async function calls together.
+
+```javascript
+fetchTrainer(trainerName)
+  .then(response => {
+    const trainerData = response.body;
+
+    return fetchPokemonFor({ trainerId: trainerData.id });
+  })
+  .then(response => {
+    // I want trainerData, but it is now out of scope...
+  });
+```
+
+But in the last `then()` you want access to both the `trainerData` and the
+`pokemonData`. So, how do you pass both the `trainerData` and the resolved
+response of `fetchPokemonFor()` through to that last `then()`.
+
+```javascript
+fetchTrainer(trainerName)
+  .then(response => {
+    const trainerData = response.body;
+
+    return Promise.all([
+      trainerData,
+      fetchPokemonFor({ trainerId: trainerData.id })
+    ]);
+  })
+  .then(([trainerData, pokemonResponse]) => {
+    const pokemonData = pokemonResponse.body;
+
+    // do something with trainerData and pokemonData
+  });
+```
+
+`Promise.all` allows us to resolve and pass multiple promises. If any of the
+values in the array argument is not a promise, it simply passes it through.