A way to "cache" a value in Puppeteer's waitForFunction?-CodePudding

Is there a way to "cache" a value in Puppeteer's browser-based functions?

The callback passed to page.waitForFunction( .. ) is running on every DOMMutation from the puppeteer option polling: "mutation". So it could potentially run 500 times and execute const listEl = document.querySelector("#list") 500 times.

I was wondering if there is a way to cache listEl when it's found so that next time the callback is invoked querySelector("#listEl") does not have to run again and the cached value inside listEl is used.

await page.waitForFunction(
    () => {
      const listEl = document.querySelector("#list");
    },
    {
      polling: "mutation",
    }
  );
})();

The callback inside waitForFunction( ..) has no access to variables outside the function. Because the callback runs (injected) inside Browser context and the outside environment is node.js.

CodePudding user response：

You could just make it a window property:

window.listEl = window.listEl || document.querySelector("#list")

CodePudding user response：

Well you could use localStorage. As puppeteer is using chromium, localStorage is therefore supported.

await page.evaluate(() => {
  localStorage.setItem('key', 'value');
});

You could even probably pass the localStorage value through different executions on a same domain via userDataDir launch option.

const browser = await puppeteer.launch({
  userDataDir: './temp/',
  // ...
});