add an example about reusing a browser

Use javascript with cookies, which is a pretty common way to "save" work between separate visits to the same site in the same browser. This also shows how to use timeouts properly, without having the timeout affect the entire browser's process. Fixes chromedp#548.
clindet · Jan 6, 2020 · ff70bc3 · ff70bc3
1 parent aa5cc87
commit ff70bc3
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Showing 2 changed files with 48 additions and 1 deletion.
diff --git a/example_test.go b/example_test.go
@@ -12,6 +12,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"github.com/chromedp/cdproto/cdp"
 	"github.com/chromedp/cdproto/dom"
@@ -92,6 +93,52 @@ func ExampleExecAllocator() {
 	// DevToolsActivePort has 2 lines
 }
 
+func ExampleNewContext_reuseBrowser() {
+	ts := httptest.NewServer(writeHTML(`
+<body>
+<script>
+	// Show the current cookies.
+	var p = document.createElement("p")
+	p.innerText = document.cookie
+	p.setAttribute("id", "cookies")
+	document.body.appendChild(p)
+
+	// Override the cookies.
+	document.cookie = "foo=bar"
+</script>
+</body>
+	`))
+	defer ts.Close()
+
+	// create a new browser
+	ctx, cancel := chromedp.NewContext(context.Background())
+	defer cancel()
+
+	// start the browser without a timeout
+	if err := chromedp.Run(ctx); err != nil {
+		panic(err)
+	}
+
+	for i := 0; i < 2; i++ {
+		// look at the page twice, with a timeout set up; we skip
+		// cancels for the sake of brevity
+		ctx, _ := context.WithTimeout(ctx, time.Second)
+		ctx, _ = chromedp.NewContext(ctx)
+		var cookies string
+		if err := chromedp.Run(ctx,
+			chromedp.Navigate(ts.URL),
+			chromedp.Text("#cookies", &cookies),
+		); err != nil {
+			panic(err)
+		}
+		fmt.Printf("Cookies at i=%d: %q\n", i, cookies)
+	}
+
+	// Output:
+	// Cookies at i=0: ""
+	// Cookies at i=1: "foo=bar"
+}
+
 func ExampleNewContext_manyTabs() {
 	// new browser, first tab
 	ctx1, cancel := chromedp.NewContext(context.Background())

diff --git a/util_test.go b/util_test.go
@@ -29,7 +29,7 @@ const dumpJS = `(function dump(n, prefix, indent, nodeIDs) {
 	var s = '';
 	if (typeof n.localName !== 'undefined') {
 		s = n.localName;
-	} 
+	}
 	if (s === '' && typeof n.nodeName !== 'undefined') {
 		s = n.nodeName;
 	}