renames

2017-05-25 11:56:32 +03:00 · 2017-05-25 11:56:32 +03:00 · 455d300d8d
commit 455d300d8d
parent 787d58a83f
280 changed files with 2 additions and 2 deletions
--- a/6-async/04-promise-api/02-promise-errors-as-results-2/solution.md
+++ b/6-async/04-promise-api/02-promise-errors-as-results-2/solution.md
--- a/6-async/04-promise-api/02-promise-errors-as-results-2/solution.view/index.html
+++ b/6-async/04-promise-api/02-promise-errors-as-results-2/solution.view/index.html
@ -0,0 +1,29 @@
+<!DOCTYPE HTML>
+<html>
+<body>
+
+  <script>
+
+    let urls = [
+      'https://api.github.com/users/iliakan',
+      '/',
+      'http://no-such-url'
+    ];
+
+    Promise.all(
+        urls.map(url => fetch(url).catch(err => err))
+      )
+      .then(responses => Promise.all(
+        // if it's an error then pass on
+        // otherwise response.json() and catch errors as results
+        responses.map(r => r instanceof Error ? r : r.json().catch(err => err))
+      ))
+      .then(results => {
+        alert(results[0].name); // Ilya Kantor
+        alert(results[1]); // SyntaxError: Unexpected token < in JSON at position 0
+        alert(results[2]); // TypeError: failed to fetch (text may vary)
+      });
+  </script>
+
+</body>
+</html>
--- a/6-async/04-promise-api/02-promise-errors-as-results-2/source.view/index.html
+++ b/6-async/04-promise-api/02-promise-errors-as-results-2/source.view/index.html
@ -0,0 +1,33 @@
+<!DOCTYPE HTML>
+<html>
+<body>
+
+  <script>
+
+    // the whole promise chain fails with an error here
+    // change that:
+    // make errors appear as members of the results array
+
+    let urls = [
+      'https://api.github.com/users/iliakan',
+      // this URL is HTML page, it's invalid JSON, so response.json() fails
+      '/',
+      // this URL is invalid, so fetch fails
+      'http://no-such-url'
+    ];
+
+    // Fix it:
+    Promise.all(urls.map(url => fetch(url)))
+      .then(responses => Promise.all(
+        responses.map(r => r.json())
+      ))
+      // Demo output (no need to change):
+      .then(results => {
+        alert(results[0].name); // Ilya Kantor
+        alert(results[1]); // SyntaxError: Unexpected token < in JSON at position 0
+        alert(results[2]); // TypeError: failed to fetch (text may vary)
+      });
+  </script>
+
+</body>
+</html>
--- a/6-async/04-promise-api/02-promise-errors-as-results-2/task.md
+++ b/6-async/04-promise-api/02-promise-errors-as-results-2/task.md
@ -0,0 +1,34 @@
+# Fault-tolerant fetch with JSON
+
+Improve the solution of the previous task <info:task/promise-errors-as-results>. Now we need not just to call `fetch`, but to load the JSON objects from given URLs.
+
+Here's the example code to do that:
+
+```js run
+let urls = [
+  'https://api.github.com/users/iliakan',
+  'https://api.github.com/users/remy',
+  'https://api.github.com/users/jeresig'
+];
+
+// make fetch requests
+Promise.all(urls.map(url => fetch(url)))
+  // map each response to response.json()
+  .then(responses => Promise.all(
+    responses.map(r => r.json())
+  ))
+  // show name of each user
+  .then(users => {  // (*)
+    for(let user of users) {
+      alert(user.name);
+    }
+  });
+```
+
+The problem is that if any of requests fails, then `Promise.all` rejects with the error, and we loose results of all the other requests. So the code above is not fault-tolerant, just like the one in the previous task.
+
+Modify the code so that the array in the line `(*)` would include parsed JSON for successful requests and error for errored ones.
+
+Please note that the error may occur both in `fetch` (if the network request fails) and in `response.json()` (if the response is invalid JSON). In both cases the error should become a member of the results object.
+
+The sandbox has both of these cases.