onnorh · January 4, 2024 19:43 · Jul 24, 2019 · Jul 18, 2019
diff --git a/polling.js b/polling.js
@@ -0,0 +1,65 @@
+const axios = require('axios').default;
+
+function getAPIClient() {
+  const axiosConfig = {
+    baseURL: 'https://csrng.net/csrng/csrng.php',
+    timeout: 5000,
+  };
+
+  return axios.create(axiosConfig);
+}
+
+function getData() {
+  const client = getAPIClient();
+  return client.get('/?min=0&max=100');
+}
+
+// create a promise that resolves after a short delay
+function delayPromise(ms) {
+  return new Promise(function(resolve) {
+    setTimeout(resolve, ms);
+  });
+}
+
+// cb is the callback function
+// interval is how often to poll
+// timeout is how long to poll waiting for a result (0 means try forever)
+function poll(cb, predicate, errorHandler, interval, timeout) {
+  let start = Date.now();
+
+  function run() {
+    return cb().then(function({ data }) {
+      console.log('data:', data);
+      if (predicate(data)) {
+        // we know we're done here, return from here whatever you
+        // want the final resolved value of the promise to be
+        return data;
+      } else {
+        if (timeout !== 0 && Date.now() - start > timeout) {
+          errorHandler();
+        } else {
+          // run again with a short delay
+          return delayPromise(interval).then(run);
+        }
+      }
+    });
+  }
+  return run();
+}
+
+function isGreaterThan90([number]) {
+  return number.random > 90;
+}
+
+function errorHandler() {
+  throw new Error('timeout error on poll');
+}
+
+function logResult(data) {
+  data = JSON.stringify(data, null, 2);
+  console.log(`result: ${data}`);
+}
+
+poll(getData, isGreaterThan90, errorHandler, 1000, 30 * 1000)
+  .then(logResult)
+  .catch(console.error);