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Worker

Worker 类代表 WebWorker。worker 事件在页面对象上触发，以指示工作线程创建。当工作线程消失时，工作线程对象上会触发 close 事件。

¥The Worker class represents a WebWorker. worker event is emitted on the page object to signal a worker creation. close event is emitted on the worker object when the worker is gone.

page.on('worker', worker => {
  console.log('Worker created: ' + worker.url());
  worker.on('close', worker => console.log('Worker destroyed: ' + worker.url()));
});

console.log('Current workers:');
for (const worker of page.workers())
  console.log('  ' + worker.url());

方法​

¥Methods

evaluate​

Added in: v1.8 worker.evaluate

返回 pageFunction 的返回值。

¥Returns the return value of pageFunction.

如果传递给 worker.evaluate() 的函数返回 Promise，那么 worker.evaluate() 将等待 Promise 解析并返回其值。

¥If the function passed to the worker.evaluate() returns a Promise, then worker.evaluate() would wait for the promise to resolve and return its value.

如果传递给 worker.evaluate() 的函数返回非 可串行化 值，则 worker.evaluate() 返回 undefined。Playwright 还支持传输一些 JSON 无法序列化的附加值：-0、NaN、Infinity、-Infinity。

¥If the function passed to the worker.evaluate() returns a non-Serializable value, then worker.evaluate() returns undefined. Playwright also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity.

用法

¥Usage

await worker.evaluate(pageFunction);
await worker.evaluate(pageFunction, arg);

参数

¥Arguments

在工作环境中评估的功能。

¥Function to be evaluated in the worker context.

传递给 pageFunction 的可选参数。

¥Optional argument to pass to pageFunction.

返回

¥Returns

evaluateHandle​

Added in: v1.8 worker.evaluateHandle

将 pageFunction 的返回值作为 JSHandle 返回。

¥Returns the return value of pageFunction as a JSHandle.

worker.evaluate() 和 worker.evaluateHandle() 之间的唯一区别是 worker.evaluateHandle() 返回 JSHandle。

¥The only difference between worker.evaluate() and worker.evaluateHandle() is that worker.evaluateHandle() returns JSHandle.

如果传递给 worker.evaluateHandle() 的函数返回 Promise，那么 worker.evaluateHandle() 将等待 Promise 解析并返回其值。

¥If the function passed to the worker.evaluateHandle() returns a Promise, then worker.evaluateHandle() would wait for the promise to resolve and return its value.

用法

¥Usage

await worker.evaluateHandle(pageFunction);
await worker.evaluateHandle(pageFunction, arg);

参数

¥Arguments

在工作环境中评估的功能。

¥Function to be evaluated in the worker context.

传递给 pageFunction 的可选参数。

¥Optional argument to pass to pageFunction.

返回

¥Returns

url​

Added in: v1.8 worker.url

用法

¥Usage

worker.url();

返回

¥Returns

事件​

¥Events

on('close')​

Added in: v1.8 worker.on('close')

当该专用 WebWorker 终止时触发。

¥Emitted when this dedicated WebWorker is terminated.

用法

¥Usage

worker.on('close', data => {});

事件数据

¥Event data