AsyncArray

artem-karpenko · Apr 20, 2019 · 48a4bdc · 48a4bdc
1 parent 0460497
commit 48a4bdc
Showing 1 changed file with 67 additions and 0 deletions.
diff --git a/async-iteration.js b/async-iteration.js
@@ -0,0 +1,67 @@
+async function print(msg, delay) {
+    return new Promise((resolve, reject) => {
+        setTimeout(() => {
+        console.log("delay:" + msg);
+        resolve(msg);
+    }, delay);
+});
+}
+
+async function f() {
+    for await (let a of [print("1", 3000), print("2", 1000)]) {
+        console.log("loop:", a);
+    }
+}
+
+// f();
+
+const SyncArray = {
+    [Symbol.iterator]: function() {
+        let i = 3;
+        return {
+            next: () => {
+            if (i > 0) {
+            i--;
+            return {
+                value: i
+            };
+        } else {
+            return {
+                done: true
+            }
+        }
+    }
+    };
+    }
+};
+
+/**
+ * Allows sequential iteration over array of promises
+ */
+class AsyncArray {
+    constructor(data) {
+        this.data = data;
+    }
+    [Symbol.asyncIterator]() {
+        let iterator = this.data.values();
+        return {
+            next: () => {
+            let result = iterator.next();
+        if (result.value) {
+            return result.value().then(value => {
+                return {value};
+        });
+        }
+        return {done: true};
+    }
+    };
+    }
+}
+
+async function asyncLoop() {
+    for await (let a of new AsyncArray([print.bind(null, "1", 3000), print.bind(null, "2", 1000)])) {
+        console.log("loop:", a);
+    }
+}
+
+asyncLoop();