puppeteer/test/assets/beforeunload.html

<script>
window.addEventListener('beforeunload', event => {
  event.returnValue = 'Leave?';
});
</script>
feat(Page): add option to run 'beforeunload' when closing the page (#2478) Today, `page.close()` method doesn't run page's beforeunload listeners. This way users can be sure that `page.close()` actually closes the page. This patch adds an optional `runBeforeUnload` option to the `page.close()` method that would run beforeunload listeners. Note: running beforeunload handlers might cancel page closing. Fixes #2386. 2018-05-02 22:51:45 +00:00			`<script>`
			`window.addEventListener('beforeunload', event => {`
			`event.returnValue = 'Leave?';`
			`});`
			`</script>`