Set localstorage items before page loads in puppeteer?

javascript local-storage puppeteer
christoffee picture christoffee · Aug 10, 2018 · Viewed 11.2k times · Source

We have some routing logic that kicks you to the homepage if you dont have a JWT_TOKEN set... I want to set this before the page loads/before the js is invoked.

how do i do this ?

Answer

Everettss picture Everettss · Aug 11, 2018

You have to register localStorage item like this:

await page.evaluate(() => {
  localStorage.setItem('token', 'example-token');
});

You should do it after page page.goto - browser must have an url to register local storage item on it. After this, enter the same page once again, this time token should be here before the page is loaded.

Here is a fully working example:

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

const html = `
<html>
  <body>
    <div id="element"></div>

    <script>
      document.getElementById('element').innerHTML = 
        localStorage.getItem('token') ? 'signed' : 'not signed';
    </script>
  </body>
</html>`;

http
  .createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/html' });
    res.write(html);
    res.end();
  })
  .listen(8080);

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.goto('http://localhost:8080/');

  await page.evaluate(() => {
    localStorage.setItem('token', 'example-token');
  });

  await page.goto('http://localhost:8080/');

  const text = await page.evaluate(
    () => document.querySelector('#element').textContent
  );

  console.log(text);
  await browser.close();

  process.exit(0);
})();

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