added async filter

Author: varun93

async-filter.js

@@ -0,0 +1,25 @@
+const asyncCall = async element => {
+  return new Promise((resolve, reject) => {
+    setTimeout(() => {
+      resolve(element % 2 === 0);
+    }, 5000);
+  });
+};
+
+const asyncFilter = async (array, callback) => {
+  const data = await Promise.all(
+    array.map(async element => {
+      const predicate = await callback(element);
+      return predicate ? element : undefined;
+    })
+  );
+
+  return data.filter(item => item !== undefined);
+};
+
+// driver code
+const input = [1, 2, 3, 4, 5, 6];
+
+asyncFilter(input, asyncCall).then(response => {
+  console.log(response);
+});