> Markdown version of [Executing JavaScript](https://vaadin.com/docs/v10/flow/advanced/tutorial-execute-javascript). Section index: [llms.txt](https://vaadin.com/docs/v10/flow/llms.txt)

# Executing JavaScript

You can use server-side Java to execute simple JavaScript snippets in the browser. You can also pass parameters to the executed script as variables named $0, $1 and so on. The framework automatically serializes and escapes the parameter values.

```java
public static void logElementSize(String name, Element element) {
    Page page = UI.getCurrent().getPage();

    page.executeJavaScript(
            "console.log($0 + ' size:', $1.offsetWidth, $1.offsetHeight)",
            name, element);
}
```

Supported parameter types are `String`, `Boolean`, `Integer`, `Double`, `JsonValue` and `Element`. The script is executed after the DOM tree has been updated based on server-side changes. The parameter value will be `null` for an element parameter that is not attached after the update (according to the server-side DOM).

> **Note:** The script is executed asynchronously, so you can’t directly pass values back to the server.