How do I deal with dynamically loaded content when using GoQuery?

Dealing with dynamically loaded content, often referred to as AJAX content, can be a challenge when using GoQuery in Go, because GoQuery itself doesn't have the capability to execute JavaScript or wait for content to be loaded dynamically as it would in a browser environment. GoQuery works by parsing the static HTML content that you download through an HTTP request.

When you are faced with a situation where the content is loaded dynamically by JavaScript, you need to employ different strategies:

1. Analyze Network Traffic

Use browser developer tools to inspect the network traffic and determine if the dynamic content is being fetched via separate AJAX requests. If that's the case, you can directly make HTTP requests to those URLs to retrieve the data.

2. Use an HTTP Client to Make Requests

In Go, you can use the net/http package to make requests to the endpoints identified in the first step.

Here is an example of making an HTTP request to a JSON API and then parsing the JSON:

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {
    // URL of the AJAX endpoint
    ajaxURL := "https://example.com/api/data"

    // Make a GET request to the endpoint
    resp, err := http.Get(ajaxURL)
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    // Read the response body
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }

    // Parse JSON data
    var data interface{}
    err = json.Unmarshal(body, &data)
    if err != nil {
        panic(err)
    }

    // Now you can work with the data variable which holds the parsed JSON
    fmt.Println(data)
}

3. Use a Headless Browser

For pages where the content is heavily dependent on JavaScript execution, you can use a headless browser that can execute JavaScript and render the page just like a regular browser. Libraries like chromedp or tools like Selenium can be used in Go for this purpose.

Here's a basic example of using chromedp to retrieve dynamic content:

package main

import (
    "context"
    "fmt"
    "github.com/chromedp/chromedp"
)

func main() {
    // Create a new context
    ctx, cancel := chromedp.NewContext(context.Background())
    defer cancel()

    // URL of the page with dynamic content
    var url = "https://example.com"

    // Variable to hold the page's HTML
    var pageHTML string

    // Run tasks
    // Navigate to the page, wait for an element to be visible, and then get the outer HTML of the page
    err := chromedp.Run(ctx,
        chromedp.Navigate(url),
        // You could use chromedp.WaitVisible to wait for a specific element
        // chromedp.WaitVisible(`#someElement`, chromedp.ByID),
        chromedp.OuterHTML("html", &pageHTML),
    )
    if err != nil {
        panic(err)
    }

    // pageHTML now contains the HTML of the page after JavaScript has been executed
    fmt.Println(pageHTML)
}

4. Evaluate the JavaScript

In some cases, you might be able to directly evaluate the JavaScript code that generates the content. This requires a deep understanding of the page's scripts and is generally a more complex and fragile approach.

Remember, when scraping dynamic content, always respect the terms of use of the website, and the legality of scraping in your jurisdiction. It's also important to consider the ethical implications and the load your requests may place on the website's servers.