Add useragent javascript example

examples/useragent.js

@@ -0,0 +1,49 @@
+import { browser } from 'k6/x/browser/async';
+import { check } from 'https://jslib.k6.io/k6-utils/1.5.0/index.js';
+
+export const options = {
+  scenarios: {
+    ui: {
+      executor: 'shared-iterations',
+      options: {
+        browser: {
+            type: 'chromium',
+        },
+      },
+    },
+  },
+  thresholds: {
+    checks: ["rate==1.0"]
+  }
+}
+
+export default async function() {
+  let context = await browser.newContext({
+    userAgent: 'k6 test user agent',
+  })
+  let page = await context.newPage();
+  await check(page, {
+    'user agent is set': async p => {
+        const userAgent = await p.evaluate(() => navigator.userAgent);
+        return userAgent.includes('k6 test user agent');
+    }
+  });
+  await page.close();
+  await context.close();
+
+  context = await browser.newContext();
+  check(context.browser(), {
+    'user agent does not contain headless': b => {
+        return b.userAgent().includes('Headless') === false;
+    }
+  });
+
+  page = await context.newPage();
+  await check(page, {
+    'chromium user agent does not contain headless': async p => {
+        const userAgent = await p.evaluate(() => navigator.userAgent);
+        return userAgent.includes('Headless') === false;
+    }
+  });
+  await page.close();
+}