Add beforeScreenShot option (#425)

Co-authored-by: Sindre Sorhus <[email protected]>

readme.md

@@ -180,6 +180,34 @@ Default: `{}`
 
 Options passed to [`puppeteer.launch()`](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#puppeteerlaunchoptions).
 
+##### beforeScreenshot
+
+Type: `Function`
+
+The specified function is called right before the screenshot is captured, as well as before any bounding rectangle is calculated as part of `options.element`. It receives the Puppeteer [`Page` instance](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#class-page) as the first argument and the [`browser` instance](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#class-browser) as the second argument. This gives you a lot of power to do custom stuff. The function can be async.
+
+Note: Make sure to not call `page.close()` or `browser.close()`.
+
+```js
+const Pageres = require('pageres');
+
+(async () => {
+	await new Pageres({
+		delay: 2,
+		beforeScreenshot: async (page, browser) => {
+			await checkSomething();
+			await page.click('#activate-button');
+			await page.waitForSelector('.finished');
+		}
+	})
+		.src('https://github.com/sindresorhus/pageres', ['480x320', '1024x768', 'iphone 5s'], {crop: true})
+		.dest(__dirname)
+		.run();
+
+	console.log('Finished generating screenshots!');
+})();
+```
+
 ### pageres.src(url, sizes, options?)
 
 Add a page to screenshot.

source/index.ts

@@ -1,5 +1,6 @@
 import {promisify} from 'util';
 import {parse as parseUrl} from 'url'; // eslint-disable-line node/no-deprecated-api
+import type {BeforeScreenshot} from 'capture-website';
 import path = require('path');
 import fs = require('fs');
 import os = require('os');
@@ -162,6 +163,34 @@ export interface Options {
 	@default {}
 	*/
 	readonly launchOptions?: captureWebsite.Options['launchOptions'];
+
+	/**
+	The specified function is called right before the screenshot is captured. It receives the Puppeteer [`Page` instance](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#class-page) as the first argument and the [`browser` instance](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#class-browser) as the second argument. This gives you a lot of power to do custom stuff. The function can be async.
+
+	Note: Make sure to not call `page.close()` or `browser.close()`.
+
+	@example
+	```
+	const Pageres = require('pageres');
+
+	(async () => {
+		await new Pageres({
+			delay: 2,
+			beforeScreenshot: async (page, browser) => {
+				await checkSomething();
+				await page.click('#activate-button');
+				await page.waitForSelector('.finished');
+			}
+		})
+			.src('https://github.com/sindresorhus/pageres', ['480x320', '1024x768', 'iphone 5s'], {crop: true})
+			.dest(__dirname)
+			.run();
+
+		console.log('Finished generating screenshots!');
+	})();
+	```
+	*/
+	readonly beforeScreenShot?: BeforeScreenshot;
 }
 
 /**
@@ -495,7 +524,8 @@ export default class Pageres extends EventEmitter {
 			userAgent: options.userAgent,
 			headers: options.headers,
 			darkMode: options.darkMode,
-			launchOptions: options.launchOptions
+			launchOptions: options.launchOptions,
+			beforeScreenShot: options.beforeScreenShot
 		};
 
 		if (options.username && options.password) {