Error: Evaluation failed: ReferenceError: res is not defined

Question

I have a scope problem in node with puppeteer. I cannot send what is obtained in the evaluate object of puppeteer, because I get: Error: Evaluation failed: ReferenceError: res is not defined I need help.

const express = require('express');
const path = require('path'); // NEW
const puppeteer = require('puppeteer');
const fs = require('fs');

const config = require('../src/config.js');
const app = express();
const port = process.env.PORT || 3006;
const DIST_DIR = path.join(__dirname, '../dist'); // NEW
const HTML_FILE = path.join(DIST_DIR, 'index.html'); // NEW

app.use(express.static(DIST_DIR)); // NEW
app.get('/api', (req, res) => {
  res.send(mockResponse);
});
app.get('/getapi', async (req, res) => {
  req.setTimeout(500000);

  var pal= req.query.palabra;
  function randomIntFromInterval(min, max) { // min and max included
    return Math.floor(Math.random() * (max - min + 1) + min);
  }

  const next_class = 'snByac';

      const browser = await puppeteer.launch({
      headless: false,
    });
      const page = await browser.newPage();

      await page.goto('https://adwords.google.com/ko/KeywordPlanner/Home?', {waitUntil: 'networkidle2'});
      await page.waitFor(randomIntFromInterval(10000,25000));
      await page.type('input[name=identifier]', config.mail);
      await page.click('span.' + next_class);
      await page.waitFor(randomIntFromInterval(20000,23000));
      await page.type('input[name=password]', config.password)
      await page.click('span.' + next_class)
      await page.waitFor(randomIntFromInterval(37000,45000));
      await page.click('[icon="arrow_forward"]')
      await page.waitFor(randomIntFromInterval(3800,6000));
      await page.type('[aria-autocomplete="list"]', pal)
      await page.waitFor(randomIntFromInterval(1400,2400));
      await page.keyboard.press('Enter');
      await page.waitFor(randomIntFromInterval(5000,14000));
      await page.keyboard.press('Enter');
      var hotelJson = {};
      await page.evaluate(() => {
      var hotelsElms = document.querySelectorAll('.keyword._ngcontent-vyt-82');
      hotelsElms.forEach((hotelelement) => {
       hotelJson.name = hotelelement.querySelector('span.keyword._ngcontent-vyt-82').innerText;
        });
      res.json(hotelJson);
});


        await browser.close();

});
app.get('/', (req, res) => {
 res.sendFile(HTML_FILE); // EDIT
});
app.listen(port, function () {
 console.log('App listening on port: ' + port);
});
//app.setTimeout(500000);

I have also tried putting "res.json (hotelJson);" outside of the "evaluate" object but returns an empty json, it is as if "hotelJson" could not be assigned within the scope of the "evaluate" function and then reverted empty, I tried to fill it with false data and it also returns empty.

Solution

Official document - The method returns a Promise which resolves to the return value of pageFunction.

This mean you can get back a value in "outside" of evaluate function.

//...
const result = await page.evaluate(() => {
    var hotelsElms = document.querySelectorAll('.keyword._ngcontent-vyt-82');
    var hotelJson = {};
    hotelsElms.forEach((hotelelement) => {
        hotelJson[name] = hotelelement.querySelector('span.keyword._ngcontent-vyt-82').innerText;
    });
    return hotelJson; // return value to "out site", assign `hotelJson` to `result`
});

// response the data to the client
res.json(result);

// ...

Comments

[MechaCode]

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