docs(examples/element-html) add example that uses page.evalute and pa…

…ge.evaluateHandle

examples/element-html.js

@@ -0,0 +1,46 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Gets HTML of the top search element from developers.google.com/web
+ * using page.evaluate() and page.evaluateHandle() to show the difference between these two methods
+ **/
+
+'use strict';
+
+const puppeteer = require('puppeteer');
+
+(async() => {
+  const browser = await puppeteer.launch();
+  const page = await browser.newPage();
+
+  await page.goto('https://developers.google.com/web/');
+
+  const elementHandle = await page.$('#top-search');
+  const pageFunction = element => element.innerHTML;
+
+  // page.evaluate() evaluates pageFunction in page context and returns javascript-object
+  const jsObject = await page.evaluate(pageFunction, elementHandle);
+
+  // page.evaluateHandler() evaluates pageFunction in page context and returns in-page object (JSHandle)
+  const jsHandle = await page.evaluateHandle(pageFunction, elementHandle);
+
+  // to show the difference between two methods
+  console.log(`jsObject is NOT equal to jsHandle: ${jsObject !== jsHandle}`); // prints true
+  console.log(`jsObject is equal to jsHandle.jsonValue(): ${jsObject === (await jsHandle.jsonValue())}`); // prints true
+
+  await browser.close();
+})();