多个选择器上的木偶等待选择器

使任何元素存在

您可以使用 querySelectorAll 和 waitForFunction 共同解决这个问题。使用带逗号的所有选择器将返回与任何选择器匹配的所有节点。

await page.waitForFunction(() => 
  document.querySelectorAll('Selector1, Selector2, Selector3').length
);

现在这只会回来 true 如果有某个元素,它不会返回与哪些元素匹配的选择器。

使用如何 Promise.race() 就像我在下面的代码片段中所做的一样,不要忘记 { visible: true } 中的选项 page.waitForSelector() 方法

public async enterUsername(username:string) : Promise<void> {
    const un = await Promise.race([
        this.page.waitForSelector(selector_1, { timeout: 4000, visible: true })
        .catch(),
        this.page.waitForSelector(selector_2, { timeout: 4000, visible: true })
        .catch(),
    ]);

    await un.focus();
    await un.type(username);
}

根据Abu Taher博士的建议,我得出以下结论:

// One of these SELECTORs should appear, we don't know which
await page.waitForFunction((sel) => { 
    return document.querySelectorAll(sel).length;
},{timeout:10000},SELECTOR1 + ", " + SELECTOR2); 

// Now see which one appeared:
try {
    await page.waitForSelector(SELECTOR1,{timeout:10});
}
catch(err) {
    //check for "not found" 
    let ErrMsg = await page.evaluate((sel) => {
        let element = document.querySelector(sel);
        return element? element.innerHTML: null;
    },SELECTOR2);
    if(ErrMsg){
        //SELECTOR2 found
    }else{
        //Neither found, try adjusting timeouts until you never get this...
    }
};
//SELECTOR1 found

我也遇到了类似的问题,于是选择了这个简单的解决方案:

helpers.waitForAnySelector = (page, selectors) => new Promise((resolve, reject) => {
  let hasFound = false
  selectors.forEach(selector => {
    page.waitFor(selector)
      .then(() => {
        if (!hasFound) {
          hasFound = true
          resolve(selector)
        }
      })
      .catch((error) => {
        // console.log('Error while looking up selector ' + selector, error.message)
      })
  })
})

然后使用它:

const selector = await helpers.waitForAnySelector(page, [
  '#inputSmsCode', 
  '#buttonLogOut'
])

if (selector === '#inputSmsCode') {
  // We need to enter the 2FA sms code. 
} else if (selector === '#buttonLogOut') {
  // We successfully logged in
}

另一种简单的解决方案是从更CSS的角度来解决这个问题。 waitForSelector 似乎遵循 CSS selector list rules 因此,基本上您可以通过使用逗号来选择多个CSS元素。

try {    
    await page.waitForSelector('.selector1, .selector2',{timeout:1000})
} catch (error) {
    // handle error
}

在Puppeter中,您可以简单地使用多个选择器,这些选择器由coma分隔,如下所示:

const foundElement = await page.waitForSelector('.class_1, .class_2');

返回的元素将是页面中找到的第一个元素的elementHandle。

接下来,如果您想知道找到了哪个元素,可以获得如下类名:

const className = await page.evaluate(el => el.className, foundElement);

在您的情况下,应该可以使用类似的代码:

const foundElement = await page.waitForSelector([SELECTOR1,SELECTOR2].join(','));
const responseMsg = await page.evaluate(el => el.innerText, foundElement);
if (responseMsg == "No records found"){ // Your code here }

进一步使用 Promise.race() 通过包装它,只需检查索引的进一步逻辑:

// Typescript
export async function racePromises(promises: Promise<any>[]): Promise<number> {
  const indexedPromises: Array<Promise<number>> = promises.map((promise, index) => new Promise<number>((resolve) => promise.then(() => resolve(index))));
  return Promise.race(indexedPromises);
}

// Javascript
export async function racePromises(promises) {
  const indexedPromises = promises.map((promise, index) => new Promise((resolve) => promise.then(() => resolve(index))));
  return Promise.race(indexedPromises);
}

用法:

const navOutcome = await racePromises([
  page.waitForSelector('SELECTOR1'),
  page.waitForSelector('SELECTOR2')
]);
if (navigationOutcome === 0) {
  //logic for 'SELECTOR1'
} else if (navigationOutcome === 1) {
  //logic for 'SELECTOR2'
}

将上面的一些元素组合到助手方法中,我构建了一个命令,允许我创建多个可能的选择器结果,并处理第一个要解决的问题。

/**
 * @typedef {import('puppeteer').ElementHandle} PuppeteerElementHandle
 * @typedef {import('puppeteer').Page} PuppeteerPage
 */

/** Description of the function
  @callback OutcomeHandler
  @async
  @param {PuppeteerElementHandle} element matched element
  @returns {Promise<*>} can return anything, will be sent to handlePossibleOutcomes
*/

/**
 * @typedef {Object} PossibleOutcome
 * @property {string} selector The selector to trigger this outcome
 * @property {OutcomeHandler} handler handler will be called if selector is present
 */

/**
 * Waits for a number of selectors (Outcomes) on a Puppeteer page, and calls the handler on first to appear,
 * Outcome Handlers should be ordered by preference, as if multiple are present, only the first occuring handler
 * will be called.
 * @param {PuppeteerPage} page Puppeteer page object
 * @param {[PossibleOutcome]} outcomes each possible selector, and the handler you'd like called.
 * @returns {Promise<*>} returns the result from outcome handler
 */
async function handlePossibleOutcomes(page, outcomes)
{
  var outcomeSelectors = outcomes.map(outcome => {
    return outcome.selector;
  }).join(', ');
  return page.waitFor(outcomeSelectors)
  .then(_ => {
    let awaitables = [];
    outcomes.forEach(outcome => {
      let await = page.$(outcome.selector)
      .then(element => {
        if (element) {
          return [outcome, element];
        }
        return null;
      });
      awaitables.push(await);
    });
    return Promise.all(awaitables);
  })
  .then(checked => {
    let found = null;
    checked.forEach(check => {
      if(!check) return;
      if(found) return;
      let outcome = check[0];
      let element = check[1];
      let p = outcome.handler(element);
      found = p;
    });
    return found;
  });
}

要使用它,您只需调用并提供一系列可能的结果及其选择器/处理程序:

 await handlePossibleOutcomes(page, [
    {
      selector: '#headerNavUserButton',
      handler: element => {
        console.log('Logged in',element);
        loggedIn = true;
        return true;
      }
    },
    {
      selector: '#email-login-password_error',
      handler: element => {
        console.log('password error',element);
        return false;
      }
    }
  ]).then(result => {
    if (result) {
      console.log('Logged in!',result);
    } else {
      console.log('Failed :(');
    }
  })

我刚开始 木偶演员 ,并且遇到了相同的问题,因此我想创建一个满足相同用例的自定义函数。

功能如下:

async function waitForMySelectors(selectors, page){
    for (let i = 0; i < selectors.length; i++) {
        await page.waitForSelector(selectors[i]);
    }
}

函数中的第一个参数接收选择器数组,第二个参数是我们在其中执行等待过程的页面。

调用函数,如下例所示:

var SelectorsArray = ['#username', '#password'];
await waitForMySelectors(SelectorsArray, page);

虽然我还没有对它进行任何测试,但它似乎很实用。

如果木偶程序方法无法完成请求,则可能会抛出错误。例如,第页。如果选择器在给定的时间段内不匹配任何节点,waitForSelector(选择器[,选项])可能会失败。

对于某些类型的错误,Puppeter使用特定的错误类。这些类可以通过require('puppeter/Errors')获得。

支持的类列表:

TimeoutError

处理超时错误的示例:

const {TimeoutError} = require('puppeteer/Errors');

// ...

try {
  await page.waitForSelector('.foo');
} catch (e) {
  if (e instanceof TimeoutError) {
    // Do something if this is a timeout.
  }
}