waitForEvent(event[, optionsOrPredicate])

This is documentation for the next version of K6. For the latest stable release, go to the latest version.

Documentation

Open source

Waits for the event to fire and returns its value. If a predicate function has been set it will pass the value to the predicate function, which must return true for the promise to resolve.

Parameter	Type	Default	Description
event	string	`null`	Name of event to wait for. Currently the `'page'` event is the only one that is supported.
optionsOrPredicate	function\|object	`null`	Optional. If it’s a function, the `'page'` event data will be passed to it and it must return `true` to continue.
optionsOrPredicate.predicate	function	`null`	Optional. Function that will be called when the `'page'` event is emitted. The event data will be passed to it and it must return `true` to continue.
optionsOrPredicate.timeout	number	`30000`	Optional. Maximum time to wait in milliseconds.

Returns

Type	Description
`Promise<Page>`	A Promise that fulfills with a page object when the `page` event has been emitted.

Example

This API is useful when you want to wait for the new page to open after clicking on a link that opens in a new tab.

import { browser } from 'k6/browser';

export const options = {
  scenarios: {
    ui: {
      executor: 'shared-iterations',
      options: {
        browser: {
          type: 'chromium',
        },
      },
    },
  },
};

export default async function () {
  const page = await browser.newPage();

  await page.goto('https://test.k6.io/');

  await page.keyboard.down('ControlOrMeta');

  // Open the link in a new tab with the help of the meta key.
  // Wait for the new page to be created.
  const browserContext = browser.context();
  const [newTab] = await Promise.all([
    browserContext.waitForEvent('page'),
    await page.locator('a[href="/my_messages.php"]').click(),
  ]);

  await page.keyboard.up('ControlOrMeta');

  // Wait for the new page (tab) to load.
  await newTab.waitForLoadState('load');

  // Take screenshots of each page.
  await page.screenshot({ path: `screenshot-page.png` });
  await newTab.screenshot({ path: `screenshot-newTab.png` });

  await newTab.close();
  await page.close();
}

Here’s an example working with the predicate:

import { browser } from 'k6/browser';

export const options = {
  scenarios: {
    browser: {
      executor: 'shared-iterations',
      options: {
        browser: {
          type: 'chromium',
        },
      },
    },
  },
};

export default async function () {
  const context = await browser.newContext();

  // Call waitForEvent with a predicate which will return true once at least
  // one page has been created.
  let counter = 0;
  const promise = await context.waitForEvent('page', {
    predicate: (page) => {
      if (++counter >= 1) {
        return true;
      }
      return false;
    },
  });

  // Now we create a page.
  const page = await context.newPage();

  // Wait for the predicate to pass.
  await promise;
  console.log('predicate passed');

  await page.close();
}