Page.evaluateOnNewDocument() 方法

¥Page.evaluateOnNewDocument() method

添加将在以下场景之一调用的函数：

¥Adds a function which would be invoked in one of the following scenarios:

• 每当页面被导航时

  ¥whenever the page is navigated

• 每当附加或导航子框架时。在这种情况下，该函数在新附加的框架的上下文中调用。

  ¥whenever the child frame is attached or navigated. In this case, the function is invoked in the context of the newly attached frame.

在创建文档之后但在运行其任何脚本之前调用该函数。这对于修改 JavaScript 环境很有用，例如 种子 Math.random。

¥The function is invoked after the document was created but before any of its scripts were run. This is useful to amend the JavaScript environment, e.g. to seed Math.random.

签名

¥Signature

class Page {
  abstract evaluateOnNewDocument<
    Params extends unknown[],
    Func extends (...args: Params) => unknown = (...args: Params) => unknown,
  >(
    pageFunction: Func | string,
    ...args: Params
  ): Promise<NewDocumentScriptEvaluation>;
}

参数

¥Parameters

范围	类型	描述
pageFunction	功能 | 字符串	要在浏览器上下文中评估的函数
args	参数	要传递给 pageFunction 的参数

Returns:

Promise<NewDocumentScriptEvaluation>

示例

¥Example

在页面加载之前覆盖 navigator.languages 属性的示例：

¥An example of overriding the navigator.languages property before the page loads:

// preload.js

// overwrite the `languages` property to use a custom getter
Object.defineProperty(navigator, 'languages', {
  get: function () {
    return ['en-US', 'en', 'bn'];
  },
});

// In your puppeteer script, assuming the preload.js file is
// in same folder of our script.
const preloadFile = fs.readFileSync('./preload.js', 'utf8');
await page.evaluateOnNewDocument(preloadFile);