在 Puppeteer 中无法检测页面上是否存在元素

Question

I'm writing a bot for a pokemon MMORPG game. I wrote a script to login to my account and move around, the problem is that when I move around, I sometimes find a pokemon and then a new div is created which has the pokemon's data. I also get a button (with the id '#catch') to catch the pokemon. So I wrote the script such that it would check for the #catch button. Here's my code

while (true) {
    await page.waitFor(500);
    await page.keyboard.press("ArrowDown");
    if ((await page.$("input#catch")) != null) {
      console.log("Pokemon Found!");
    } else {
      console.log("No Pokemon Found");
    }

however, I get 'No Pokemon Found' every single time, even if there is one.

Answer 1

You can check if element exist by using vanilla javascript

if(document.getElementById('catch').length > 0){
    console.log("Pokemon Found!");
}else{
    console.log("No Pokemon Found");
}

Answer 2

I've found putting 'WaitFor's in code not very reliable or efficient. If you make them too small, if there is a delay from networking or other reasons, then you have failures. If you make them huge, then your code take for ever to do. In my code I've been waitForSelector . It has a wait/timeout that can be enlarged.

Example:

async clickSomeButton(cssSelector) {
    if (await page.waitForSelector(cssSelector, 10000)) {
        await page.click(cssSelector);
        return;
    }
    return fail;
}