How can I check if selector exists in puppeteer?

Question

In Puppeteer, how can I check if, for example, #idProductType exists and if not, set producttype to ""? I tried many many things but it doesn't work.

const urls = [myurls, ...]
const productsList = [];
for (let i = 0; i < urls.length; i++) {
    const url = urls[i];
    await Promise.all([
        page.goto(url),
        page.waitForNavigation({ waitUntil: 'networkidle0' }),
    ]);

    let products = await page.evaluate(() => {

  //here i want to test if #idProductType exists do : 
        let producttype = document.querySelector('#idProductType').innerText;
  //else 
        let producttype = "";
  //and same thing for other selectors

        let productsubtype = document.querySelector('#idProductSubType').innerText;
        let product = document.querySelector('#idProduct').innerText;
        let description = document.querySelector('td.js-orderModelVer').innerText;
        let reference = document.querySelector('td.text-nowrap').innerText;
        let prixpub = document.querySelector('td.text-nowrap.text-right.js-pricecol-msrp').innerText;
        let dispo = document.querySelector('td.text-nowrap.text-center.js-pricecol-availability').innerText;
        let retire = document.querySelector('td.js-retired-filler-cell').innerText;

        let results = [];
        results.push({
            producttype: producttype,
            productsubtype: productsubtype,
            product: product,
            description: description,
            reference: reference,
            prixpub: prixpub,
            dispo: dispo,
            retire: retire
        })
        return results
    })
    productsList.push(products);
}

Answer 1

return innerText or empty string if not found:

let productType = await page.evaluate(() => {
  let el = document.querySelector(".foo")
  return el ? el.innerText : ""
})

Answer 2

You can use page.$(selector) which is similar to document.querySelector(selector)

let producttype = (await page.$('#idProductType')) || "";

Answer 3

Puppeteer throws an error when could not find a matched element.

So to confirm the existence,

try {
  await page.$(selector)
  // Does exist
} catch {
  // Does not
}

Or to make whether it exists a flag

const exists = await page.$eval(selector, () => true).catch(() => false)