consolidation of various example repos/gists

javascript/async/README.md

@@ -0,0 +1,10 @@
+# Async
+
+Copy to a file (e.g test.js) and run with:
+node test.js
+
+Result should be something like this:
+
+![image showing the result](./image.png)
+
+PS: To clarify. Both loops run at the same time, to test remove the Math.max bit of the second loop) but the log on line 69 is delayed because it is wrapped in a function which uses await to make sure that the loop has finished before (allowing for sync-like programming)

javascript/async/async.js

@@ -0,0 +1,72 @@
+/**
+ * log a message with an iso datetime
+ * @param {*} msg msg to log
+ */
+const log = (msg) => {
+  console.log(msg, new Date().toISOString());
+};
+
+/**
+ * sleep for a certain amount of ms
+ * @param {*} ms ms to sleep
+ */
+const sleep = (ms) => {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+};
+
+/**
+ * "asyncForEach" method on every array, allowing for async functionality on any array
+ */
+if (!Array.prototype.asyncForEach) {
+  Array.prototype.asyncForEach = async function (func) {
+    "use strict";
+
+    if (this == null) {
+      throw new TypeError(
+        "Array.prototype.asyncForEach called on null or undefined"
+      );
+    }
+
+    if (typeof func !== "function") {
+      throw new TypeError();
+    }
+
+    var t = Object(this);
+
+    return await Promise.allSettled(
+      t.map(async (item) => {
+        return await func(item);
+      })
+    );
+  };
+}
+
+// array is not in order, this will be used to test
+const items = [200, 1000, 400, 300];
+
+// starting test
+log("Starting async test");
+
+// because of the sleep we expect the responses from small -> large
+items.asyncForEach(async (item) => {
+  await sleep(item);
+  log(item);
+});
+
+// because the previous foreach is async we expect this to run immediately.
+log("after async foreach (or before? because async..)");
+
+async function testWithAwait() {
+  await items.asyncForEach(async (item) => {
+    // this will sleep for whatever the largest amount in items is + currentItem.
+    // this will make sure test items are displayed AFTER the first batch of items.
+    // this doesn't impact the result because the code IN the foreach will still run async (just with a delayed console.log)
+    await sleep(Math.max(...items) + item);
+    log(`Async with wait: ${item}`);
+  });
+
+  // because of the await on line 60 this will only run AFTER the async foreach has been handled
+  log("after testWithAwait");
+}
+
+testWithAwait();