Selenium Webdriver错误[UnhandledPromiseRejectionWarning]

Question

刚开始通过"Mozilla MDN web docs“进入selenium World，遇到了一个错误。请帮助我们继续前进。

正在尝试获取元素的文本属性，如p、title、alert...但它不能通过。

​

var webdriver = require('selenium-webdriver'),
	By = webdriver.By,
	until = webdriver.until;

var driver = new webdriver.Builder()
	.forBrowser('chrome')
	.build();

driver.get('http://mdn.github.io/learning-area/tools-testing/cross-browser-testing/accessibility/native-keyboard-accessibility.html');


var button = driver.findElement(By.css('button:nth-of-type(1)'));


button.click();


var alert = driver.switchTo().alert();

alert.getText().then(function(text) {
	console.log('Alert text is \'' + text + '\'');
})

alert.accept();

​

    uptimizators-MacBook-Air:study uptimizator$ node quick_test
(node:1941) UnhandledPromiseRejectionWarning: NoSuchAlertError: no such alert
  (Session info: chrome=78.0.3904.97)
    at Object.throwDecodedError (/Users/uptimizator/node_modules/selenium-webdriver/lib/error.js:550:15)
    at parseHttpResponse (/Users/uptimizator/node_modules/selenium-webdriver/lib/http.js:563:13)
    at Executor.execute (/Users/uptimizator/node_modules/selenium-webdriver/lib/http.js:489:26)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at async thenableWebDriverProxy.execute (/Users/uptimizator/node_modules/selenium-webdriver/lib/webdriver.js:699:17)
(node:1941) 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(). (rejection id: 1)
(node:1941) [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.
(node:1941) UnhandledPromiseRejectionWarning: NoSuchAlertError: no such alert
  (Session info: chrome=78.0.3904.97)
    at Object.throwDecodedError (/Users/uptimizator/node_modules/selenium-webdriver/lib/error.js:550:15)
    at parseHttpResponse (/Users/uptimizator/node_modules/selenium-webdriver/lib/http.js:563:13)
    at Executor.execute (/Users/uptimizator/node_modules/selenium-webdriver/lib/http.js:489:26)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at async thenableWebDriverProxy.execute (/Users/uptimizator/node_modules/selenium-webdriver/lib/webdriver.js:699:17)
(node:1941) 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(). (rejection id: 2)

Answer 1

几乎所有的东西都会返回一个承诺，所以你应该“等待”它们：

; (async function(){
  await driver.get('http://mdn.github.io/learning-area/tools-testing/cross-browser-testing/accessibility/native-keyboard-accessibility.html');

  var button = driver.findElement(By.css('button:nth-of-type(1)'));

  await button.click();

  var alert = driver.switchTo().alert();

  var text = await alert.getText()
  console.log('Alert text is \'' + text + '\'');

  await alert.accept()
})()

我不明白为什么文档是错误的，我猜它在旧的节点版本上是不同的。