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事件

介绍

Introduction

Playwright 允许监听网页上发生的各种类型的事件,例如网络请求、子页面的创建、专用工作线程等。有多种方法可以订阅此类事件,例如等待事件或添加或删除事件监听器。

Playwright allows listening to various types of events happening on the web page, such as network requests, creation of child pages, dedicated workers etc. There are several ways to subscribe to such events such as waiting for events or adding or removing event listeners.

等待事件

Waiting for event

大多数时候,脚本需要等待特定事件的发生。以下是一些典型的事件等待模式。

Most of the time, scripts will need to wait for a particular event to happen. Below are some of the typical event awaiting patterns.

使用 page.waitForRequest() 等待指定 url 的请求:

Wait for a request with the specified url using page.waitForRequest():

// Start waiting for request before goto. Note no await.
const requestPromise = page.waitForRequest('**/*logo*.png');
await page.goto('https://wikipedia.org');
const request = await requestPromise;
console.log(request.url());

等待弹出窗口:

Wait for popup window:

// Start waiting for popup before clicking. Note no await.
const popupPromise = page.waitForEvent('popup');
await page.getByText('open the popup').click();
const popup = await popupPromise;
await popup.goto('https://wikipedia.org');

添加/删除事件监听器

Adding/removing event listener

有时,事件是随机发生的,我们不需要等待它们,而是需要对其进行处理。Playwright 支持订阅和取消订阅事件的传统语言机制:

Sometimes, events happen in random time and instead of waiting for them, they need to be handled. Playwright supports traditional language mechanisms for subscribing and unsubscribing from the events:

page.on('request', request => console.log(`Request sent: ${request.url()}`));
const listener = request => console.log(`Request finished: ${request.url()}`);
page.on('requestfinished', listener);
await page.goto('https://wikipedia.org');

page.off('requestfinished', listener);
await page.goto('https://www.openstreetmap.org/');

添加一次性监听器

Adding one-off listeners

如果某个事件需要处理一次,有一个方便的 API:

If a certain event needs to be handled once, there is a convenience API for that:

page.once('dialog', dialog => dialog.accept('2021'));
await page.evaluate("prompt('Enter a number:')");