Ultralight is built on JavaScriptCore-- the same high-performance JavaScript engine used by Safari/WebKit on macOS and iOS.

We expose low-level C bindings to JavaScriptCore so that you can seamlessly integrate your native code with JavaScript running on a page.

> 📘 C++ Wrapper for JavaScriptCore
>
> We offer a wrapper to simplify usage from C++. See [JSHelpers.h in the AppCore API](/api/cpp/1_4_0/_j_s_helpers_8h_source.html)

## Using the JavaScriptCore API

To use the JavaScriptCore API in your code, just include `<JavaScriptCore/JavaScript.h>`:

```c
#include <JavaScriptCore/JavaScript.h>
```

You can browse the API headers for JavaScriptCore [by clicking here](https://github.com/ultralight-ux/Ultralight-API/tree/master/JavaScriptCore).

## Common API Types

| API Type | Description |
| :--- | :--- |
| **JSContextRef** | A JavaScript execution context, you will need this to make most calls in JavaScriptCore. |
| **JSValueRef** | The base type for all JavaScript values (eg, `Number`, `String`, `Object`, `Boolean`, etc.). **This is a garbage-collected type.** |
| **JSObjectRef** | A JavaScript object-- this value is technically typedef'd to the same underlying type as `JSValueRef` and can be passed anywhere that accepts a `JSValueRef`. **This is a garbage-collected type.** |
| **JSStringRef** | A raw UTF-16 string buffer for passing strings to/from JavaScript. |
| **JSClassDefinition** | Used to create custom JavaScript objects that wrap native objects. |