How do I execute custom JavaScript on a page with headless_chrome (Rust) in Rust?

To execute custom JavaScript on a page with headless_chrome in Rust, you'll need to use the evaluate method provided by the Tab struct after navigating to the desired page. Here's an example of how you can do it:

First, make sure you have added headless_chrome to your Cargo.toml:

[dependencies]
headless_chrome = "0.9.0" # Make sure to use the latest version

Next, you can write a Rust program that will launch a browser, navigate to a page, and execute custom JavaScript.

Here's an example:

extern crate headless_chrome;

use headless_chrome::{Browser, LaunchOptionsBuilder};
use std::sync::Arc;

fn main() -> Result<(), failure::Error> {
    // Launch a new browser
    let browser = Browser::new(
        LaunchOptionsBuilder::default()
            .headless(true)
            .build()
            .expect("Failed to launch browser"),
    )?;

    // Connect to a new tab
    let tab = browser.wait_for_initial_tab()?;

    // Navigate to the page
    tab.navigate_to("http://example.com")?
       .wait_until_navigated()?;

    // Define your custom JavaScript code as a string
    let js_code = r#"
        (() => {
            // Custom JavaScript code goes here
            return document.title;
        })();
    "#;

    // Execute your custom JavaScript code
    let result = tab.evaluate(js_code, true)?;

    // `result` contains the return value of the executed JavaScript
    println!("Page title is: {:?}", result.value);

    Ok(())
}

This example demonstrates how to open http://example.com, execute a JavaScript snippet that retrieves the document's title, and print it out.

Please note that the headless_chrome crate may be updated, or its API might change over time, so make sure to check the documentation or the repository for the latest usage examples and best practices. Also, the error handling is basic in this example. In a production environment, you would want to handle errors more gracefully.

Here are some key points to consider:

• headless_chrome provides a high-level API to control Chrome or Chromium in headless mode.
• The evaluate method runs JavaScript code in the context of the current page and returns a Result with the outcome.
• You can specify whether you want the expression to return a value by passing true or false as the second argument to evaluate.
• Error handling is done using the Result and Option types, which you should handle appropriately in your code.