Introduction To Puppeteer

Introduction to Puppeteer

In this post, we will give you information about Introduction to Puppeteer – onlinecode. Here we will give you detail about Introduction to Puppeteer – onlinecode And how to use it also give you a demo for it if it is necessary.

Puppeteer is Google’s officially supported library for controlling Chrome from Node.js. You can open
Chrome from Node.js, navigate to Google, search for something, and see the results. Or you can run Puppeteer in headless mode and make it run in the background.

For example, here’s how you can make Chrome load Google’s home page using Puppeteer and Node.js:

const puppeteer = require('puppeteer');

run().then(() => console.log('Done')).catch(error => console.log(error));

async function run() {
  // Setting 'headless: false' opens up a browser
  // window so you can watch what happens.
  const browser = await puppeteer.launch({ headless: false });

  // Open a new page and navigate to google.com
  const page = await browser.newPage();
  await page.goto('https://google.com');

  // Wait 5 seconds
  await new Promise(resolve => setTimeout(resolve, 5000));

  // Close the browser and exit the script
  await browser.close();
}

The output looks like this:

Evaluating JavaScript for Introduction to Puppeteer

Puppeteer pages have a handy evaluate() function that lets you execute JavaScript in the Chrome window. The evaluate() function is the most flexible way to interact with Puppeteer, because it lets you control Chrome using browser APIs like document.querySelector().

For example, the below script searches for “JavaScript” on Google, and gets the top 10 results.

const puppeteer = require('puppeteer');

// Run in the background (headless mode)
const browser = await puppeteer.launch({ headless: true });

// Navigate to Google
const page = await browser.newPage();
await page.goto('https://google.com');

// Type "JavaScript" into the search bar
await page.evaluate(() => {
  document.querySelector('input[name="q"]').value = 'JavaScript';
});

// Click on the "Google Search" button and wait for the page to load
await Promise.all([
  page.waitForNavigation(),
  page.evaluate(() => {
    document.querySelector('input[value="Google Search"]').click();
  })
]);

// Get all the search result URLs
const links = await page.evaluate(function getUrls() {
  return Array.from(document.querySelectorAll('a cite').values()).
    map(el => el.innerHTML);
});

await browser.close();

Using Puppeteer with a Local Web Server

Because Node.js uses an event loop, it is easy to start an Express
server and connect Puppeteer to your Express server in the same
script. This means it is easy to test Vue apps with Puppeteer.

const express = require('express');
const puppeteer = require('puppeteer');

// Start an Express app that renders a Vue app with a counter
const app = express();
app.get('/', function(req, res) {
  res.send('
  <html>
    <body>
      <script src="https://unpkg.com/vue/dist/vue.js"></script>

      <div id="content"></div>

      <script type="text/javascript">      
        const app = new Vue({
          data: () => ({ count: 0 }),
          template: '
            <div>
              <div id="count">
                Count: {{count}}
              </div>
              <button v-on:click="++count">Increment</button>
            </div>
          '
        });
        app.$mount('#content');
      </script>
    </body>
  </html>
  ');
});
const server = await app.listen(3000);

// Run in the background (headless mode)
const browser = await puppeteer.launch({ headless: true });
const page = await browser.newPage();
await page.goto('http://localhost:3000');

// Load the current count
let count = await page.evaluate(() => {
  return document.querySelector('#count').innerHTML.trim();
});
count; // 'Count: 0'

// Increment the count and check that the counter was incremented
await page.evaluate(() => {
  document.querySelector('button').click();
});

count = await page.evaluate(() => {
  return document.querySelector('#count').innerHTML.trim();
});
count; // 'Count: 1'

await browser.close();
await server.close();

JavaScript Fundamentals for Introduction to Puppeteer

JavaScript is a programming language that is used to create interactive web pages. It is a client-side scripting language, which means that it runs on the user’s browser. JavaScript can be used to add animation, interactivity, and functionality to web pages.

Here are some of the fundamentals of JavaScript:

Variables: Variables are used to store data. They are declared using the var keyword.
Data types: JavaScript has a variety of data types, including strings, numbers, booleans, objects, and arrays.
Operators: Operators are used to perform operations on data.
Control flow statements: Control flow statements allow you to control the order in which your code is executed.
Functions: Functions are blocks of code that can be reused.
Objects: Objects are used to store data in key-value pairs.
Arrays: Arrays are used to store data in a sequential order.
Events and event handlers: Events are notifications that are sent by the browser when something happens, such as when the user clicks on an element or moves the mouse over an element. Event handlers are functions that are called in response to an event.
DOM manipulation: The Document Object Model (DOM) is a tree-like structure that represents the elements of a web page. JavaScript can be used to manipulate the DOM to change the appearance or behavior of a web page.