Create async-await.js

backend/tutorials/async-await.js

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+// https://javascript.info/async-await
+
+// A async function always returns a promise. Other values are wrapped in a resolved promise automatically.
+
+async function f1() {
+    return 1;
+  }
+  
+  f1().then(console.log); // 1
+
+// The keyword await makes JavaScript wait until that promise settles and returns its result.
+// It can be used in async functions only
+// Let’s emphasize: await literally suspends the function execution until the promise settles, 
+// and then resumes it with the promise result.
+async function f2() {
+
+    let promise = new Promise((resolve, reject) => {
+      setTimeout(() => resolve("done!"), 1000)
+    });
+  
+    let result = await promise; // wait until the promise resolves (*)
+  
+    console.log(result); // "done!"
+  }
+  
+  f2();