我怎么能传递这个变量来从我的模块中使用它？

Question

I've set a basic puppeteer code to automate chrome. And I'm trying to pass the page variable as parameter to my module method using mymodule.foo(page) but it fails throwing the error you can see below:

The goal is to be able to use puppeteer objects like page from other modules.

E:\scripts\node\myproject\mymodule.js:3
    await page.evaluateOnNewDocument(() => {
          ^^^^

SyntaxError: Unexpected identifier
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:607:28)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)
    at Function.Module._load (module.js:491:3)
    at Module.require (module.js:587:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (E:\scripts\node\myproject\app.js:3:18)
PS E:\scripts\node\myproject>

This is the file app.js :

// app.js
const puppeteer = require('puppeteer');

const mymodule = require('./mymodule');

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

  await mymodule.foo(page);

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

This is the file mymodule.js :

UPDATE: I've updated this file to add async to the foo function. But then If I try to use await page.goto('http://www.google.com'); with await I get the same error. So I tried to add another async doing page.evaluateOnNewDocument(async () Then it runs, open the browser, but it doesn't navigate to the page, neither wait.

// mymodule.js
module.exports = {
  foo: async function (page) {
    await page.evaluateOnNewDocument(async () => {
      await page.goto('http://www.google.com');
      await page.waitFor(10000);  // That's Evil, I know
    });
  }
};

UPDATE 2: This is the actual code (suggested by @Ｈｏｎｇａｒｃ) I'm using, that doesn't throw errors, but doesn't work yet.

module.exports = {
  foo: function (page) {
    return page.evaluateOnNewDocument(async () => {
      await page.goto('http://www.google.com');
      await page.waitFor(10000);  // That's Evil, I know
    });
  }
};

Another approach would be acceptable, whilst we can use ie. page.goto(<url>) inside of foo function of mymodule . If it work, it'll be ok.

Answer 1

Let's face it, the following function will run a code on the browser context

page.evaluateOnNewDocument

The error is not on the module itself, but how you are using it. page Object is not available on the browser context. So calling it is not the solution.

If you want to use page. in another module, you can safely do it this way,

// mymodule.js
module.exports = {
  foo: async function (page) {
      await page.goto('http://www.google.com');
      await page.waitFor(10000);
  }
};

Also make sure you have node version 7.6 or higher.

Answer 2

You need mark your function is async to use await . Try this:

// mymodule.js
module.exports = {
  foo: async function (page) {
    await page.evaluateOnNewDocument(async () => {
      await page.goto('http://www.google.com');
      await page.waitFor(10000);
    });
  }
};

This code will fix syntax of your code, but it wrong about logic.

• You don't need await in module.exports.foo of mymodule.js .
• async don't have competence use for function inside it.

You can try:

// mymodule.js
module.exports = {
  foo: function (page) {
    return page.evaluateOnNewDocument(async () => {
      await page.goto('http://www.google.com');
      await page.waitFor(10000);
    });
  }
};