Add async iterator support

.eslintrc.json

@@ -1,6 +1,10 @@
 {
   "env": {
-    "node": true
+    "node": true,
+    "es6": true
+  },
+  "parserOptions": {
+    "ecmaVersion": 2018
   },
   "extends": "eslint:recommended",
   "rules": {

index.d.ts

@@ -10,6 +10,7 @@ declare class FeedParser extends stream.Transform {
     options: FeedParser.Options;
 
     read(): FeedParser.Item | null;
+    [Symbol.asyncIterator](): AsyncGenerator<FeedParser.Item>;
     resumeSaxError(): void;
 
     on(event: 'meta', listener: (meta: FeedParser.Meta) => void): this;

lib/feedparser/index.js

@@ -1237,4 +1237,45 @@ FeedParser.prototype._flush = function (done) {
  * @typedef {import('readable-stream').Transform & FeedParserState} FeedParserInstance
  */
 
+/** @this {FeedParserInstance} */
+FeedParser.prototype[Symbol.asyncIterator] = async function* () {
+  var resolve = null;
+  var error = null;
+  var ended = false;
+
+  function onReadable() {
+    if (resolve) { resolve(); resolve = null; }
+  }
+  function onEnd() {
+    ended = true;
+    if (resolve) { resolve(); resolve = null; }
+  }
+  function onError(err) {
+    error = err;
+    if (resolve) { resolve(); resolve = null; }
+  }
+
+  this.on('readable', onReadable);
+  this.on('end', onEnd);
+  this.on('error', onError);
+
+  try {
+    while (true) {
+      var item;
+      while ((item = this.read()) !== null) {
+        yield item;
+      }
+      if (ended) break;
+      if (error) throw error;
+      await new Promise(function (r) { resolve = r; });
+      resolve = null;
+      if (error) throw error;
+    }
+  } finally {
+    this.removeListener('readable', onReadable);
+    this.removeListener('end', onEnd);
+    this.removeListener('error', onError);
+  }
+};
+
 exports = module.exports = FeedParser;

test/examples.js

@@ -0,0 +1,17 @@
+var FeedParser = require('../');
+
+describe('examples', function () {
+  it('should work as an async iterator', async function () {
+    var feedparser = new FeedParser();
+    var feed = __dirname + '/feeds/rss2sample.xml';
+    var items = [];
+
+    fs.createReadStream(feed).pipe(feedparser);
+
+    for await (const item of feedparser) {
+      items.push(item);
+    }
+
+    assert.equal(items.length, 4);
+  });
+});