Add Promise.withResolvers example

Author: tshemsedinov

JavaScript/d-resolvers.js

@@ -0,0 +1,46 @@
+'use strict';
+
+// Need node.js 22
+
+const sumAsync = (a, b, callback) => {
+  if (typeof a !== 'number') return;
+  if (typeof b !== 'number') return;
+  setImmediate(() => {
+    callback(a + b);
+  });
+};
+
+// Old approach
+
+(async () => {
+  let resolve, reject;
+  const promise = new Promise((resolved, rejected) => {
+    resolve = resolved;
+    reject = rejected;
+  });
+  setTimeout(reject, 1000, new Error('Timed out'));
+  sumAsync(2, 3, resolve);
+  const result = await promise;
+  console.log({ result });
+})();
+
+// Alternative approach
+
+(async () => {
+  const promise = new Promise((resolve, reject) => {
+    sumAsync(4, 5, resolve);
+    setTimeout(reject, 1000, new Error('Timed out'));
+  });
+  const result = await promise;
+  console.log({ result });
+})();
+
+// New approach
+
+(async () => {
+  const { promise, resolve, reject } = Promise.withResolvers();
+  setTimeout(reject, 1000, new Error('Timed out'));
+  sumAsync(6, 7, resolve);
+  const result = await promise;
+  console.log({ result });
+})();