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

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

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+# 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.