schnerd · April 18, 2018 03:21 · Apr 18, 2018
diff --git a/lazy-load-puppeteer.js b/lazy-load-puppeteer.js
@@ -0,0 +1,35 @@
+function wait (ms) {
+  return new Promise(resolve => setTimeout(() => resolve(), ms));
+}
+
+export default async function capture(browser, url) {
+  // Load the specified page
+  const page = await browser.newPage();
+  await page.goto(url, {waitUntil: 'load'});
+
+  // Get the height of the rendered page
+  const bodyHandle = await page.$('body');
+  const { height } = await bodyHandle.boundingBox();
+  await bodyHandle.dispose();
+
+  // Scroll one viewport at a time, pausing to let content load
+  const viewportHeight = page.viewport().height;
+  let viewportIncr = 0;
+  while (viewportIncr + viewportHeight < height) {
+    await page.evaluate(_viewportHeight => {
+      window.scrollBy(0, _viewportHeight);
+    }, viewportHeight);
+    await wait(20);
+    viewportIncr = viewportIncr + viewportHeight;
+  }
+
+  // Scroll back to top
+  await page.evaluate(_ => {
+    window.scrollTo(0, 0);
+  });
+
+  // Some extra delay to let images load
+  await wait(100);
+
+  return await page.screenshot({type: 'png'});
+}