如何使用 nodeJS 在 puppeteer 中调用异步函数之外的函数

Question

how do I call a function passing the page object outside async method in puppeteer.

I want to implement a functionality where if a certain value is found on page it should play a music. I have defined playmusic() functionality outside async method .

const puppeteer = require('puppeteer');

const playmusic = ()=>{
   page.goto('http://www.noiseaddicts.com/free-samples-mp3/?id=2544');
   page.click('span.map_play');
}

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

 
  await page.goto('DesiredURL');
  const pricing = await page.evaluate(()=>{
    let pricesOnPage=document.querySelectorAll(".span_price_wrap");
    const priceList=[...pricesOnPage];
    return priceList.map(h=>h.innerText);
    
  });
  console.log(pricing[1]);

  if(pricing[1]>=2316)
  {
    await page.evaluate(() => {
      playmusic ();
    });
  }

 await browser.close();
})();

I m getting below error

\index.js
2346.75
(node:17316) UnhandledPromiseRejectionWarning: Error: Evaluation failed: ReferenceError: playmusic is not defined
    at __puppeteer_evaluation_script__:2:6
    at ExecutionContext._evaluateInternal (\jswebscrapping\node_modules\puppeteer\lib\cjs\puppeteer\common\ExecutionContext.js:217:19)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async ExecutionContext.evaluate (\jswebscrapping\node_modules\puppeteer\lib\cjs\puppeteer\common\ExecutionContext.js:106:16)
    at async index.js:24:4
(node:17316) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:17316) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

------------------------------UPDATE--------------------------------------------

Sharing the workable code: Thanks everyone for helping I have improved my code in couple of places such as

1. added wait time before and after playing the music .
2. Converted return value in float ( earlier it was treated as string )

const puppeteer = require('puppeteer');

 const playmusic = async (page)=>{
  await page.goto('http://www.noiseaddicts.com/free-samples-mp3/?id=2544');
  await page.waitFor(4000) ;
  await page.click('span.map_play');
  await page.waitFor(12000);
}

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

 
  await page.goto('MYURL');
  const pricing = await page.evaluate(()=>{
    let pricesOnPage=document.querySelectorAll(".span_price_wrap");
    const priceList=[...pricesOnPage];
    return priceList.map(h=>h.innerText);
    

  });
  console.log(pricing[1]);
  let PricingFloat= parseFloat(pricing[1]);

  if(PricingFloat<=21)
  {
    await playmusic (page);   
  }
  else
  {
    console.log("No Music for you");
  }

 await browser.close();
})();

Answer 1

You need to replace

const playmusic = ()=>{
   page.goto('http://www.noiseaddicts.com/free-samples-mp3/?id=2544');
   page.click('span.map_play');
}

by

const playmusic = (page) => {
   page.goto('http://www.noiseaddicts.com/free-samples-mp3/?id=2544');
   page.click('span.map_play');
}

and

    await page.evaluate(() => {
      playmusic ();
    });

by

    await page.evaluate(() => {
      playmusic (page);
    });

Because of range when page exists is constrained and when you define function playmusic then this function do not have access to variable page . You can read more about variables scopes in JS.

Link to a great article:

https://www.sitepoint.com/demystifying-javascript-variable-scope-hoisting/

---

UPDATE

After analyzing your code of error I think you need to add a try-catch block. For example.

try {
    await page.evaluate(() => {
      playmusic (page);
    });
} catch(e) {
   console.log(e);
   process.exit(1)
}

You should also check if the puppeteer does not have unrejected promised:

https://pptr.dev/#?product=Puppeteer&version=v5.3.0&show=api-class-page

For example, you can write:

const playmusic = async (page) => {
   await page.goto('http://www.noiseaddicts.com/free-samples-mp3/?id=2544');
   return page.click('span.map_play');
}

and in your main code:

try {
    await page.evaluate(async () => {
      try {
         await playmusic();
      } catch(e) {
          console.log(e);
          process.exit(1);
      }
    });
} catch(e) {
   console.log(e);
   process.exit(1)
}