# Introduction

`jsii` allows code in any language to naturally interact with **JavaScript** classes. It is the technology that enables
the [AWS Cloud Development Kit][cdk] to deliver polyglot libraries from a single codebase!

[cdk]: https://github.com/aws/aws-cdk

A class library written in **TypeScript** can be used in projects authored in **TypeScript** or **Javascript** (as
usual), but also in **C#** (and other languages from the _.NET_ family), **Go**, **Java**, **Python**, ... More
languages will be added in the future!

!!! warning
    Due to *JSON* marshaling costs and the absence of a distributed garbage collector feature, `jsii` modules are best
    suited for development and build tools, as opposed to performance-sensitive or resource-constrained applications.

    See [Runtime Architecture] for more information.

    [runtime architecture]: overview/runtime-architecture.md

## An example is worth a thousand words

Consider the following **TypeScript** class:

```ts
/**
 * A simple greeter, hello world style.
 */
export class Greeter {
  /**
   * Greets the designated person.
   *
   * @param name the person to greet.
   *
   * @returns a greeting.
   */
  public greet(name: string) {
    return `Hello, ${name}!`;
  }
}
```

By compiling our source module using `jsii`, we can now package it as modules in one of the supported target languages.
Each target module has the exact same API as the source. This allows users of that target language to use `Greeter` like
any other native type:

=== "C#"

    ```csharp
    var greeter = new Greeter();
    greeter.Greet("World"); // => Hello, World!
    ```

=== "Go"

    ```go
    greeter := NewGreeter()
    greeter.Greet("World") // => Hello, World!
    ```

=== "Java"

    ```java
    final Greeter greeter = new Greeter();
    greeter.greet("World"); // => Hello, World!
    ```

=== "JavaScript"

    ```java
    const greeter = new Greeter();
    greeter.greet("World"); // => Hello, World!
    ```

=== "Python"

    ```python
    greeter = Greeter()
    greeter.greet("World") # => Hello, World!
    ```

## How to use this website

The documentation in this website is separated in different topics, which can be navigated using links in the site's
header bar:

- The [Welcome](./index.md) section provides a high level overview of *jsii*.
- The [User Guides](./user-guides) section includes the following:

    - The [Library Author Guide](user-guides/lib-author) is intended for developers who are looking to author libraries
      using *jsii* to enable polyglot support for their work.
    - The [Library Consumer Guide](user-guides/lib-user) is intended for developers who are consuming libraries
      generated by *jsii* in the various supported target languages.
    - The [Language Implementation](user-guides/language-support) is intended for developers who are looking to add
      support for a new *target language* in *jsii*.

- The [Specification](specification/1-introduction) provides detailed information on the internal components of *jsii*.
- The [Architecture Decision Records](decisions/introduction) contains the log of all architectural decisions made while developing the
  *jsii* project.

## How to contribute

The [*jsii project*](https://github.com/aws/jsii) welcomes all kind of contributions. You can refer to the
[Contribution Guide](https://github.com/aws/jsii/blob/main/CONTRIBUTING.md) on GitHub to get more information about how
to contribute to the project in general.

!!! tip
    You can submit pull requests for documentation updates without leaving the comfort of your web browser!

    All pages of this website have a :material-pencil: icon on the top right of each page that links to a GitHub web
    editor for the source of the page in question.